PURPOSE: To provide a device which is used as an endoscope or a bore scope and easily compensates movement of the focal surface of a zoom lens for the change of the magnification.

CONSTITUTION: This device 1 includes an outer tube 2 which has a far end 3, which can be inserted into an unaccessible place to be examined, and a near end 4 which a user can access. The zoom lens is provided in the vicinity of the far end in the outer tube and can be operated so as to form an image on the focal surface in the puter tube with a variable magnification. The zoom lens includes an objective lens 7 fixed to the outer tube and two lenses 8 and 13 which can be moved independently of each other. A narrow and long sight means 43 is provided to see the image and is extended through the outer tube from the position of the focal surface to a position close to the near end. Operation means 29 and 32 operated by cams can be operated so as to move movable lenses for the purpose of changing the magnification and to move the sight means synchronously with the objective lens for the purpose of compensating movement of the focal surface. Thus, refocusing of this device following magnification adjustment is automatically performed.