The optical pickup apparatus and an optical disc apparatus

The invention provides an optical pickup device and an optical disc apparatus. In a small-sized optical pickup device for enabling to obtain a stable servo-signal, as well as, a focus error signal and a tracking error signal, without receiving ill influences of stray lights from other layers, when recording/reproducing a multi-layer optical disc, a reflection light from the multi-layer optical disc is divided into plural numbers of regions by a diffraction grating. And, it is divided into at least four regions, by a division line in the tangential direction of the optical disc and a division line in the radial direction thereof. Light receiving parts, for detecting either one of grating diffraction lights, i.e., a +1st dimensional grating diffraction light or a -1st dimensional grating diffraction light of a light beam entering into the at least four regions, are aligned, nearly, on a straight line in the radial direction of the optical disc, and light receiving parts for detecting the other dimensional grating diffraction light are aligned, shifting, with respect to a direction nearly coincident with a tangential direction of the optical disc.