An image forming apparatus has a cathode ray tube as a light source which is controlled by a control circuit including an image signal inverting circuit for inverting a polarity of an image signal and a vertical deflecting circuit for inverting an image formed on the cathode ray tube in a mirror image relationship on the basis of the vertical synchronizing signal. Thus, the image forming apparatus can provide two kinds of color images obtained by using a microcapsule sheet or a silver chloride sheet.