An abnormality detection device for an image forming apparatus detects an abnormality in the image forming apparatus which includes a heating belt looped around a heating roller and a fixing roller. The abnormality detection device for an image forming apparatus includes: thermistors for detecting temperatures of one widthwise end portion and the other widthwise end portion of the heating belt; a temperature difference detection section for determining whether or not a temperature difference between the temperature of the one end portion and the temperature of the other end portion which are detected by the thermistors is greater than a predetermined value; and a judgment section for judging that an abnormality has occurred in the image forming apparatus when it is determined in the temperature difference detection section that the temperature difference is greater than the predetermined value.