Abstract: An eyepiece optical system, an illuminating lamp, and a battery 2 are housed in an operation unit 2. An insertion unit in which an image transmitting optical fiber bundle and an illumination light transmitting optical fiber bundle are incorporated is detachably coupled with the operation unit through a coupling unit. The insertion unit is bent using a bending wire attached to the distal end thereof and coupled to the operation unit by a wire operating mechanism. An anti-clouding material can be disposed on a surface of the distal end of the insertion unit to protect it against clouding.