An image forming apparatus includes a microcomputer which controls components for executing an image forming operation, and sends a signal to a supervising portion when no abnormality occurs in itself. The supervising portion includes a watch-dog timer, and sends a reset signal to the microcomputer when the signal from the microcomputer is not continuously inputted for a predetermined time period or more. Accordingly, the microcomputer becomes in a reset state, and the image forming operation is stopped. A flag is not set until a predetermined time period elapses from a time that the reset signal is inputted, and therefore, the image forming operation is inhibited for the predetermined time period.