An objective lens of an optical pickup is made to move from far position to near position with respect to DVD with constant speed, and a timer counts time taken for the movement of a focus of a laser beam between recording layers of the DVD on the basis of a focus error signal obtained from this movement. In the case of the DVD of the single-layer, since the recording layer is one-layer, and there is no interlayer, count value becomes small value. While, in the case of DVD of the multi-layer, the recording layer consists of a plurality of layers, thus one or plural-interlayer exists, therefore, count value becomes large value. Accordingly, if small count value is obtained, its DVD is discriminated as DVD of the single-layer. While, if large count value is obtained, its DVD is discriminated as DVD of the multi-layer.