PURPOSE: To improve the picture quality, by suppressing time fluctuation from the leading of a data start pulse corresponding to each surface to the scanning start period to neglect the generation of jitter.

CONSTITUTION: The storage of a document signal (a) corresponding to each surface is started with a write pulse signal (e) generated in response to the scanning start period of each surface of a rotating polyhedral mirror 1, through the addition of a write signal generating circuit 8 and a delay circuit 9 to a conventional scanner, and the readout of the stored document signal (a) is started with a periodic data start pulse signal (c) corresponding to the next surface of each surface, allowing to suppress the time fluctuation of the scanning start for each surface generated due to the error of angle split of each surface of the mirror 1. The picture quality can be improved by neglecting the generation of jitter.