An image forming apparatus includes: Photoreceptors; an image carrier; a plurality of light emitting element arrays each configured to emit a light beam to a corresponding one of the photoreceptors independently; an angle adjustment unit to adjust a mounting angle of the light emitting element arrays to a frame of the image forming apparatus; a pattern forming unit to form a positional error correction pattern of each color on the image carrier; a optical detector to detect the correction pattern formed on the image carrier; a positional error calculation unit to calculate a printing skew error and a main scanning scaling error of the light emitting element arrays based on the correction pattern detected by the optical detector; a skew correction unit to correct the printing skew error detected by the positional error calculation unit; and further a main scanning scaling error correction unit.