An image forming apparatus includes a plurality of functions for forming an image, which are implemented by a power supply, a signal output unit, a control circuit, and a load operation unit operating in cooperation with one another. The load operation unit includes a sensor for detecting an abnormality. When the sensor has detected an abnormality, the image forming apparatus identifies a failure portion being a cause of the abnormality by checking failure portions of the power supply and the signal output unit, checking a failure portion of the control circuit when there is no failure portion in the power supply and the signal output unit, and checking a failure portion of the load operation unit when there is no failure portion in the control circuit.