编辑“︁BTOB”︁（章节）

=== 2020年：成員退伍及入伍 到 子團BTOB 4U 與 鎰勳退團===
2020年3月2日，星材發行個人特別專輯《[[YOOK O'clock (迷你專輯)|YOOK O'clock]]》，除收錄先前《3×2＝6》企劃中之歌曲，亦多加收錄主打曲〈那天的風（{{langx|ko|그날의 바람}}）〉，是第五位於韓國個人出道的成員<ref>{{cite news|url=https://www.koreastardaily.com/tc/news/124696|title=就是明天！BTOB 陸星材新專輯〈YOOK O’clock〉將溫暖登場|publisher=韓星網|date=2020-03-01|access-date=2020-03-01|language=zh-tw|archive-date=2020-03-01|archive-url=https://web.archive.org/web/20200301134850/https://www.koreastardaily.com/tc/news/124696|dead-url=no}}</ref>。
同月24日，Cube娛樂宣布因[[2019冠狀病毒病疫情|冠狀病毒病疫情]]影響，恩光在休假後不返回部隊於同年4月7日直接退役<ref>{{cite news|url=https://www.kpopn.com/2020/03/25/btob-eun-kwang-covid-19-protocol-discharged-without-returning-to-base|title=BTOB 隊長恩光要退伍了！受疫情影響休假後直接退伍|publisher=KPOPN|date=2020-03-26|access-date=2020-03-26|language=zh-tw|archive-date=2020-03-26|archive-url=https://web.archive.org/web/20200326064011/https://www.kpopn.com/2020/03/25/btob-eun-kwang-covid-19-protocol-discharged-without-returning-to-base|dead-url=no}}</ref>。
5月3日，星材於個人社群平台宣布在同年5月11日入伍<ref>{{cite news|title=BTOB’s Yook Sungjae Updates Fans On His Status After Early Discharge From Military Service|url=https://www.soompi.com/article/1491390wpp/btobs-yook-sungjae-updates-fans-on-his-status-after-early-discharge-from-military-service|date=2021-10-01|access-date=2021-10-01|work=Soompi|language=en|archive-date=2022-02-13|archive-url=https://web.archive.org/web/20220213080058/https://www.soompi.com/article/1491390wpp/btobs-yook-sungjae-updates-fans-on-his-status-after-early-discharge-from-military-service|dead-url=no}}</ref><ref>{{cite news|title=BTOB Aiming To Make Full-Group Comeback In February|url=https://www.soompi.com/article/1510386wpp/btob-aiming-to-make-full-group-comeback-in-february|date=2022-01-27|access-date=2022-01-27|work=Soompi|language=en|archive-date=2022-02-13|archive-url=https://web.archive.org/web/20220213080241/https://www.soompi.com/article/1510386wpp/btob-aiming-to-make-full-group-comeback-in-february|dead-url=no}}</ref>。5月6日，媒體報導炫植與星材同日入伍<ref>{{cite news|title=Ex-Momoland member Yeonwoo joins BTOB's Sungjae in MBC K-drama 'The Golden Spoon'|url=https://meaww.com/ex-momoland-member-yeonwoo-btob-sungjae-k-drama-the-golden-spoon|date=2022-02-13|access-date=2022-02-13|work=meaww.com|language=en|archive-date=2022-02-13|archive-url=https://web.archive.org/web/20220213003601/https://meaww.com/ex-momoland-member-yeonwoo-btob-sungjae-k-drama-the-golden-spoon |dead-url=no }}</ref>。5月11日，星材與炫植正式入伍<ref>{{cite news|title=Netizens & Melodys Really Excited As BTOB’s Sungjae Drops Updates After Early Military Discharge!|url=http://en.koreaportal.com/articles/50657/20211002/netizens-melodys-really-excited-btob-s-sungjae-drops-updates-early.htm|work=koreaportal|date=2021-10-02|access-date=2021-10-02|archive-date=2022-02-15|archive-url=https://web.archive.org/web/20220215004155/http://en.koreaportal.com/articles/50657/20211002/netizens-melodys-really-excited-btob-s-sungjae-drops-updates-early.htm|dead-url=no}}</ref><ref>{{cite news|title=BTOB’s Yook Sungjae And Hyunsik, PENTAGON’s Jinho Officially Discharged From The Military Today|url=https://www.soompi.com/article/1498528wpp/btobs-yook-sungjae-and-hyunsik-pentagons-jinho-officially-discharged-from-the-military-today|date=2021-11-14|access-date=2021-11-14|work=Soompi|language=en|archive-date=2022-02-13|archive-url=https://web.archive.org/web/20220213003600/https://www.soompi.com/article/1498528wpp/btobs-yook-sungjae-and-hyunsik-pentagons-jinho-officially-discharged-from-the-military-today|dead-url=no}}</ref>。

5月21日，恩光發表個人迷你專輯之先行曲〈抽屜（{{langx|ko|서랍}}）〉<ref>{{cite news|url=https://www.koreastardaily.com/tc/news/126673|title=終於等到恩光啦！下週推出迷你一輯先行曲|work=韓星網|date=2020-05-13|access-date=2020-05-13|language=zh-tw|archive-date=2020-05-20|archive-url=https://web.archive.org/web/20200520135139/https://www.koreastardaily.com/tc/news/126673|dead-url=no}}</ref>。同年6月8日，恩光發行首張個人迷你專輯《[[FoRest: Entrance]]》，是第六位於韓國個人出道的成員<ref>{{cite news|url=https://www.koreastardaily.com/tc/news/127026|title=BTOB 恩光敲定發片日期　再等不到兩週就好！|work=韓星網|date=2020-05-26|access-date=2020-05-26|language=zh-tw|archive-date=2020-06-04|archive-url=https://web.archive.org/web/20200604160156/https://www.koreastardaily.com/tc/news/127026|dead-url=no}}</ref>。
同月27日，鎰勳於個人社群平台宣布於隔日入伍，是最後一位入伍的成員。5月28日，鎰勳正式入伍<ref>{{cite news|url=https://star.ettoday.net/news/1724266|title=BTOB最後一人也要當兵了！　鄭鎰勳親證實入伍消息「好像很突然，我很抱歉」|work=ETtoday星光雲|date=2020-05-28|access-date=2020-05-28|language=zh-tw|archive-date=2020-06-10|archive-url=https://web.archive.org/web/20200610172557/https://star.ettoday.net/news/1724266|dead-url=no}}</ref>。

7月21日，炫植發表首張個人數位單曲〈留下（{{langx|ko|남아있어}}）〉，並收錄2018年於節目《[[鍵盤上的鬣狗]]》製作的歌曲〈抱著你的話（{{langx|ko|너를 안고 있으면}}）〉之音源<ref>{{cite news|url=https://www.koreastardaily.com/tc/news/128419|title=BTOB 炫植為歌迷準備驚喜　下週公開親錄伴奏的新自創曲！|publisher=韓星網|date=2020-07-16|access-date=2020-07-16|language=zh-tw|archive-date=2020-07-16|archive-url=https://web.archive.org/web/20200716144630/https://www.koreastardaily.com/tc/news/128419|dead-url=no}}</ref>。同月29日，Cube娛樂宣布因冠狀病毒病疫情影響，昌燮在休假後不返回部隊於同年8月21日直接退役<ref>{{cite news|url=https://www.koreastardaily.com/tc/news/128744|title=BTOB 李昌燮開始放假　8/21 正式退伍！|publisher=韓星網|date=2020-07-29|access-date=2020-07-29|language=zh-tw|archive-date=2020-07-29|archive-url=https://web.archive.org/web/20200729102150/https://www.koreastardaily.com/tc/news/128744|dead-url=no}}</ref>。9月9日，Cube娛樂宣布因冠狀病毒疫情影響，旼赫在休假後不返回部隊於同月12日直接退役<ref>{{cite news|url=https://www.kpopn.com/2020/09/12/btob-minhyuk-loco-hanhae-finished-military-service|title=BTOB 旼赫、LOCO、HANHAE 今天 (12日) 正式退伍！|publisher=KPOPN|date=2020-09-18|access-date=2020-09-18|language=zh-tw|archive-date=2021-05-12|archive-url=https://web.archive.org/web/20210512231456/https://www.kpopn.com/2020/09/12/btob-minhyuk-loco-hanhae-finished-military-service|dead-url=no}}</ref>。同年10月27日，正式宣布已退役成員恩光、旼赫、昌燮以及免服役的Peniel組成分隊「BTOB 4U」，為該團體的第二個子團。

11月16日，子團BTOB 4U發表首張迷你專輯《INSIDE》，主打歌曲〈Show Your Love〉為成員炫植的創作曲<ref>{{cite news|url=https://www.kpopn.com/2020/10/31/btob-new-unit-group-btob-4u|title=睽違四年！BTOB 將於11月推出新子團「BTOB 4U」|work=KPOPN|date=2020-10-31|access-date=2020-10-31|language=zh-tw|archive-date=2020-11-01|archive-url=https://web.archive.org/web/20201101021852/https://www.kpopn.com/2020/10/31/btob-new-unit-group-btob-4u|dead-url=no}}</ref>。該迷你專輯發行後，獲得13個國家的[[iTunes]]綜合專輯榜及韓流專輯榜冠軍，〈Show Your Love〉之音樂錄影帶在8小時內突破百萬觀看人次、在5日內突破千萬觀看人次、兩週內突破兩千萬，刷新BTOB的自身紀錄<ref>{{cite news|url=https://www.koreastardaily.com/tc/news/131730|title=不愧是因信賴而聽的 BTOB！小分隊 BTOB 4U 奪 13 國 iTunes 冠軍|work=韓星網|date=2020-11-18|access-date=2020-11-18|language=zh-tw|archive-date=2020-11-18|archive-url=https://web.archive.org/web/20201118103554/https://www.koreastardaily.com/tc/news/131730|dead-url=no}}</ref><ref>{{cite news|url=https://stars.udn.com/star/story/10092/5055743|title=「BTOB 4U」新歌一鳴驚人！首支單曲瀏覽率衝破兩千萬|work=噓！星聞|date=2020-12-01|access-date=2020-12-01|language=zh-tw|archive-date=2021-04-14|archive-url=https://web.archive.org/web/20210414091626/https://stars.udn.com/star/story/10092/5055743|dead-url=no}}</ref>。

12月21日，成員鎰勳被爆四、五年前吸食大麻，重創團體形象<ref>{{cite news|url=https://n.news.naver.com/article/449/0000201976|title=정일훈이 4~5년 전부터 지난해까지 지인들과 함께 여러차례 대마초를 피운 것으로 파악했습니다|date=2024-03-22|access-date=2024-03-22|archive-date=2024-03-22|archive-url=https://web.archive.org/web/20240322101535/https://n.news.naver.com/article/449/0000201976|dead-url=no}}</ref>。同月31日，Cube娛樂發表官方聲明，宣布鎰勳退出團體，BTOB未來將以6人組形式活動。