PURPOSE: To detect a scanning position surely to perform high-precision recording, by arranging a fluorescent substance in a detection position and detecting visible rays generated from the fluorescent substance.

CONSTITUTION: An ultraviolet beam 2a reflected on the reflective face of a rotary polygonal mirror 5 is scanned on a recording face 13 of a photosensitive drum 8 through a focusing lens 6. Fluorescent substances 14 and 15 which are excited by ultraviolet rays and generate visible rays are arranged in both ends of the recording face 13 so that they are irradiated with the beam 2a, and photodetectors 10 and 11 of silicon photodiodes are arranged in position where they can detect the luminescence of fluorescent substances 14 and 15, and photodetectors 10 and 11 are connected to a control circuit 12.