PURPOSE: To prevent a picture from deteriorating at connection points between image sensors by focusing an image, arriving from a screen, on plural image sensors through plural optical systems for sensor image formation.

CONSTITUTION: Light emitted from a light source and reflected at a readout line 5 on an original is passed through a lens 8 for screen image formation to form an image on a screen 7, and the light is further transmitted through the screen 7 to form an image on photodetection parts of image sensors 1a and 1b through lenses 9a and 9b for sensor image formation, thus reading the original 3 by the image sensors 1a and 1b. Light reflected by the original 3 is passed through the lens 8 for screen image formation as one system to form the image on the screen, so even if the original 3 shifts in readout position, light reflected at the same part on the original never forms overlapping images at different parts on the screen 7, and light reflected at some part on the original 3 fails in image formation.