To surely and easily reproduce address information recorded as wobble of a guide groove in an optical recording medium.

A photo-detector 20 for detecting the light returning from the optical recording medium has detection areas 21A-21D sectioned by a plurality of splitting lines 22, 23, 24. Push-pull signals (PP1-PP3) are obtained by altering the positions of the splitting lines as detection references according to the position of the light spot S of the returning light on the light receiving surface 21 of the photo-detector 20 and obtaining a difference between the light receiving signals according to each detection area divided into two by the splitting lines. The optical reader is so arranged that even when the spot of the returning light is positionally deviated on the photo-detector, in-phase components can be eliminated by altering the position of the splitting lines according to the light spot position and thereby obtaining the difference between the two light receiving signals by the detection areas split by the splitting lines.