To draw an image by assigning an image from a bit map memory to a plurality of laser light sources to divide the image, exposing a photosensitive material and joining the divided images into one integrated image.

An optical head 1 is constituted by disposing a plurality of pairs each comprising a laser light source and an optics projecting a laser spot. The imaging position of the spot from each laser light source installed in the head 1 is measured by a displacement detecting section 7 to determine a shift amount from a reference position and to memorize the shift amount in a memory section 23. The memorized value is read out by a control unit 8, and the shift amount in the y direction is compared with a current position of the sensitive material 2 which is moved by a command of a driving control section 4. The data from a bit map memory 39 read out based on the comparison result and the shift amount in the x direction of the memorized value are sent to a light source control section 9 to generate a light emission command signal for each laser light source. The laser light source receiving the command exposes the photosensitive material 2 disposed at a position opposing to the optical head. The divided images for each of the laser light source are joined and added to obtain one photolithographic image.