A side-viewing endoscope includes an elongated tube for entry in a body cavity for imaging. A wire line is contained in the elongated tube, for moving in an axial direction back and forth. A guide device is coupled with a distal end of the wire line, caused to shift between first and second positions by the wire line, for orientation in a direction crosswise to the axial direction upon being set in the second position. An input lever is disposed at a proximal end of the wire line, for moving the wire line in the axial direction. A cam mechanism is connected between the input lever and the wire line, for shifting the guide device at a first shift between the first position and an intermediate position, and shifting the guide device at a second shift smaller than the first shift between the intermediate and second positions.