PURPOSE: To perform data recording, reproducing and transfer at a high speed by placing multi-beams in the radial direction of a recording disk in parallel and simultaneously performing information recording and reproducing for every beam.

CONSTITUTION: Serial digital signal strings are divided for every plural bits by a multiplexer 2 and they pass respective modulating circuits 3, enter plural independent recording and reproducing readers 4, pass a first polarizing beam splitter 5, is converged by an objective lens 6, reach a magneto-optical disk 7 and recorded as pit strings. In order to reproduce the signals, a laser power, which is smaller than the power used in the recording, is continuously applied and the reflected beams from the disk are divided into incident and reflected light beams by the splitter 5. Then, a second polarizing splitter 8 separates the direction of magnetization, leads to signal detection photodiodes 9 and differences are taken. On the other hand, prepits, in which guide grooves and position information are beforehand included, are placed on the disk 7 and a lens 6 is controlled by the tracking and the focusing.