An image processing apparatus operable in plural operation modes is disclosed. The image processing apparatus includes: a first operation mode for driving an exposure head to form dot images on a photoconductor responsive to electric signals sent from an external unit so as to form an electrostatic latent image thereon; a second operation mode for driving the exposure head to form dot images on the photoconductor responsive to the electric signals sent from the image sensor so as to form an electrostatic latent image thereon; and a third operation mode for enabling optical means to form an image reflected from a document set on the document table onto the photoconductor so as to form an electrostatic latent image thereon. A controller executes the processes of the selected one or plural operation modes responsive to the mode selection signal, and controller executes the process of the first operation mode by priority to the other operation modes when plural operation modes including the first operation mode are selected.