The object of the invention is to provide a supervising system for image to detect a scheme at high accuracy. The supervising system for image is provided with a first portion for detecting change of time detecting the change of time in amount of feature of an image taken pictures by a image forming device, a second portion for detecting change of time in the illuminance detected by an illuminance sensor, and a scheme judging portion detecting a scheme against the image forming device in accordance with the change of time in amount of feature and the change of time in the illuminance as detected.