An endoscope main body (100) of an endoscope (10) with detachable observation unit includes a body cavity insertion section (12), at least one operating arm section (32, 34), a main body operating section (20), an arm section operating section (41), and an observation unit attachment/detachment mechanism (142, 86, 132). The body cavity insertion section includes a main body bending portion (44) at the distal end portion of the endoscope main body. The operating arm section includes arm section bending portion (38, 40) whose proximal end is connected to the distal end of the body cavity insertion section and which is operated and bent. The main body operating section includes a first operation mechanism (23) provided on the proximal end side of the body cavity insertion section to operate and bend the main body bending portion. The arm section operating section includes a second operation mechanism (41) provided on the proximal end side of the body cavity insertion section to operate and bend the arm section bending portion of the operating arm section. The observation unit attachment/detachment mechanism detachably attaches, to the body cavity insertion section, an observation unit (200) provided in the body cavity insertion section and having a camera section (226) and a signal transmission section (228) which transmits video data.
