An image forming apparatus that performs a shading correction includes a light source that emits a light beam; a light-source drive unit that drives the light source; and a light-quantity-adjustment-amount control unit that performs an adjustment of a light quantity in accordance with a shading correction curve by controlling, for the light-source drive unit, a light-quantity adjustment amount and an increase/decrease cycle of the light-quantity adjustment amount. The increase/decrease cycle is a unit of time within a time period during which the light-quantity adjustment amount increases or, decreases.