To provide an optical scanning device and an image forming apparatus including the same capable of maintaining a constant light emission amount required for image formation even when an optical element member made of resin used in a light receiving element is changed in properties or deteriorated without using complicated constitution.

In the initial state of a BD 28, a drive current Ib for an exposure laser beam to be incident on the BD 28 is lowered stepwise, and the drive current Ib in the preceding step before a level in which the light emission amount cannot be detected by the BD 28 is specified by a control part 32, and is set as a current value Ibs for setting. The control part 32 sets a detection current value Ids for emitting a detection laser beam on the basis of the current value Ibs for setting.