To regulate an effect of a stray light component of an optical beam reflected from a multilayer optical disk.

The optical recording/reproducing unit for recording and/or reproducing an information signal on an optical recording medium having a plurality of recording layers comprises a light-emitting device for illuminating a laser beam by focusing on one of a plurality of recording layers, a plurality of receiving devices 25a and 25b for receiving returning lights from a plurality of the recording layers, a discriminating means 41 for discriminating a receiving device which has less incident stray light component reflected on the recording layer other than the focused recording layer among the receiving devices 25a and 25b and a means 40 for selecting either of the receiving devices 25a and 25b based on the results discriminated by the discriminating means 41.