h for the divided light receiving surfaces and the beam spot on these light receiving surfaces is shown with the symbols sp 1 and sp1 and issue an output signal from these segmented light receiving surfaces the optical pickup 12 also performs current voltage conversion of the output signal from the segment light receiving surfaces in the processing circuit 15 further processing is performed of the output signal on which current voltage conversion was performed indicated by a b c d on the symbols assigned to the respective light receiving surfaces a focus error signal fe which varies the signal level according to the amount of defocus is generated and then output the symbols b c a d k e f k g h are indicated for the same purpose and a tracking signal te which changes the signal level in response to the amount of tracking error is generated and output the symbol k used here expresses the proportional constant the optical pickup 12 further outputs a warble signal wb shown respectively by e f g h here the signal constituents shown by e f and g h form two warble signals whose signal level is changed according to the oscillation of the pre group on the inner circumference and the pre group on the outer circumference corresponding to their respective track centers in this embodiment these two warble signals are summed and then output in this embodiment the address information is assigned to the pre group g2 and address information is commonly shared by the a track.