An image forming apparatus includes a substrate including a light emitting element and a controller for controlling driving of a light emitting element. a first chip and a second chip including the light emitting elements are mounted on the substrate. in a width direction of the substrate, the first chip and second chips are aligned in a certain area part. the controller drives the light emitting elements so that the light emission pattern of the two light emitting elements aligned in the width direction of the substrate is made different for each predetermined number of lines.