PURPOSE: To eliminate the need of leading all the luminous flux of returning light to a photodetector and to reduce the size by taking out only a part of the luminous flux of the returning light and leading it to the photodetector by means of a small optical means provided integrally with a light collecting means.

CONSTITUTION: The luminous flux separated by a microlens 9 is made incident on a light detector 4 and detected; the luminous flux separated by a microlens 11 is made incident on a light detector 6 and detected; the luminous flux separated by a microlens 10 is collected on a division line of a photodetector 5 and detected. The returning light from an optical information recording medium 8 is separated into luminous flux by the microlenses 9 to 11 integrally molded with a molded lens 7, only a part of the flux is received by photodetectors 4 to 6, and a focus error signal, a tracking error signal and an information signal are detected. Thus, a need for an optical element size beyond the cross- sectional area of the luminous flux of the returning light can be eliminated and the size of the optical head can be reduced.