An image pickup apparatus 1 has a heater device 13 including a heater 11 and a temperature sensor 12. The heater device 13 is arranged outside the effective light beam range of an objective optical system, with a predetermined air gap between the heater device and an inner circumferential surface of a rigid member 2 that holds a cover glass 3. The heater device 13 is pressed to the cover glass 3 by an elastic member 17 disposed at an outer circumferential portion of a protruding frame 22a that holds a lens 21 a at a distal end. An electrical connection portion of the heater 11 and an electrical connection portion of the temperature sensor 12 of the image pickup apparatus 1 are disposed facing each other with respect to an optical axis, on a proximal end side that is further to the rear than a distal end face of a lens 21a on a distal end side of a front group lens unit 20 that is a side on which a height of an effective light beam of the objective optical system is relatively low.
