PURPOSE: To record and reproduce an information signal with symmetrical variation in characteristic regardless of a direction of defocusing and without any deterioration in characteristic such as C/N even if a beam spot becomes elliptic.

CONSTITUTION: The plane containing the normal of the light splitting surface 4 of a beam splitter 3 which splits reflected light from a magnetooptic disk 6 and the optical axis of parallel light which is made incident on the light splitting surface is set in parallel or perpendicularly to the track direction of the magnetooptic disk 6, and a semiconductor laser 1 is set perpendicularly to or in parallel to the plane containing the normal of the light splitting surface and the optical axis of the parallel light. The characteristic of a magnetooptic signal, etc., varies symmetrically to make servocontrol hard to free and also decrease read errors of the information signal. Further, the information signal can be led without any loss and characteristics such as the C/N do not deteriorate.