An endoscope apparatus for producing a video signal by inserting an insertion portion in a body cavity of a patient and photographing a portion to be examined and for producing image information for medical diagnosis according to the video signal includes an adding memory, a position error detector, controllers, and a display. The memory sequentially adds and superposes succeeding image information signals constituting the video signal. The detector sequentially compares the adjacent image information signals on a time basis, and detects the position error information between the image information signals of at least portions of identical image area. The controllers cause the memory to start sequential additions in response to an external freeze instruction, and inhibit the sequential additions in response to a detection signal from the detector. The image information signals stored in the memory are displayed on the display.