A laser beam scanning apparatus according to the invention includes: a laser oscillating unit that outputs a laser beam; a laser beam scanning unit that performs scanning in a main scanning direction with a laser beam and irradiates the laser beam on a photosensitive member; an error signal generating unit that monitors, in APC period, intensity of a laser beam from the laser oscillating unit and generates an error signal of an error between oscillating unit output and a output reference value; a correction data generating unit that generates correction data for correcting intensity on the photosensitive member to be constant along the main scanning direction; a correction signal generating unit that subjects the correction data to D/A conversion to generate a correction signal; and a laser control signal generating unit. The correction data generated by the correction data generating unit is plural correction data for correcting sensitivity of the photosensitive member including a change in the sensitivity with time. The correction signal generating unit subjects the plural correction data outputted as a series of serial data from the correction data generating unit to D/A conversion to generate the plural correction signals.