PURPOSE:To increase a combining strength of a guided wave path and a detecting device, to arrange the detecting device on a monolithic substrate and to decrease the cost of a pick-up by detecting the return light from optical recording media with a photodetector loaded onto an optically wave guide path. CONSTITUTION:At a substrate 21 of an optical pick-up head 20, an optical wave guide path 22 is formed, and to one edge 22a of the wave guide path 22, a laser beam 24 is made incident from a semiconductor laser 23. The beam 24 is made incident through a beam splitter 26 to a convergent diffraction grating in parallel. A return light 24 from an optical disk 40 is photodetected by a photodetector 31 from the splitter 26 and supplied to a reading circuit. The photodetector 31 is formed at the guided wave path 22 on the substrate 21 and on both surfaces of a photoconductivity material 31b, electrodes 31a and 31b are arranged. The combining strength of the guided wave path 22 and the photodetector 31 is increased, the constitution of a head 10 is made simple and the cost of the optical pick-up is decreased.