6H-thieno [2,3-e] [1,2,4] triazolo [3,4-c] [1,2,4] triazine derivatives or salts thereof of the present invention have BRD4 inhibitory activity Therefore, it is useful as a medicine, especially as a prophylactic and / or therapeutic agent of the disease which BRD4 is involved in.본 발명의 6H-티에노[2,3-e][1,2,4]트리아졸로[3,4-c][1,2,4]트리아제핀 유도체 또는 그의 염은, BRD4 저해 활성을 갖기 때문에, 의약으로서, 특히 BRD4가 관여하는 질환의 예방 및/또는 치료제로서 유용하다.