An image pickup apparatus has a heater device including a heater and a temperature sensor. The heater device 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 that holds a cover glass. The heater device is pressed to the cover glass by an elastic member disposed at an outer circumferential portion of a protruding frame that holds a lens at a distal end. An electrical connection portion of the heater and an electrical connection portion of the temperature sensor of the image pickup apparatus 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 on a distal end side of a front group lens unit that is a side on which a height of an effective light beam of the objective optical system is relatively low.