An optical scanning image forming apparatus includes: a light source section; an illumination scanning section; a light detection section; a calculation section calculating a drive waveform for providing a illumination light scanning pattern; and an image drawing section drawing an image, based on detection light detected by the light detection section and image construction coordinates, the calculation section providing different light scanning patterns to the illumination scanning section and calculating distortion correction data, based on comparison between data on the detection lights detected when scanned in the different scanning patterns. An optical scanning image forming method includes: providing different light scanning patterns to an illumination scanning section which scans the illumination light from a light source section to irradiate an object with the illumination light; and calculating distortion correction data, based on comparison between data on the detection light detected when scanned in the different scanning patterns.