A disclosed optical scanning device includes a light beam generating unit configured to generate a light beam; a light beam deflecting unit configured to receive the light beam and deflect/emit the light beam with a deflecting mirror; a light beam ON/OFF control unit configured to control the light beam generating unit so that the light beam deflected by the light beam deflecting unit is turned ON/OFF in a particular light beam scanning region while the light beam is being reciprocally scanned; and a light beam scanning time measuring unit configured to obtain a measurement value by measuring a time at which the light beam passes a reference point provided on an edge part of the entire light beam scanning region that is away from a center part of the entire light beam scanning region. Timings at which the light beam is turned ON/OFF are controlled in accordance with the measurement value.