PURPOSE: To write/read data with an extrahigh resolution and to simultaneously take out multipoint information by writing/reading data in adjacent areas of an optical disk with coherent light which are transmitted through a phase optical filter or the like and have optical phases different by a prescribed extent.

CONSTITUTION: Coherent light which passes a semiconductor laser 1 and a condenser lens 2 is transmitted through a phase optical filter 3 to become coherent light which have optical phases different by π. Data is written in adjacent areas of a disk 7 by these coherent light which have optical phases different by π, and data is read out by these coherent light. Coherent light spots are discriminated based on phases even if they are close to one another beyond the Rayleigh's resolution limit, and data is written/read with a high resolution, and further, multipoint information are simultaneously taken out when a two-dimensional photoeletric detector 9 is used.