An image photographing system in which one button is used in common for a function of prompt photographing and a function of photographing after a predetermined time has elapsed, comprises a button for instructing an execution of an image photographing process, a control unit for monitoring a depression of this button, and a timer. The control unit starts up the timer by setting a first count time upon detecting the depression of the button, and starts up the timer by further setting a second count time when the first count time has elapsed before the depressed button is released, and the image photographing process is executed after the second count time has elapsed.