Abstract: A beam is irradiated to an information recording medium having land tracks and groove tracks alternately formed on a track formed in turn on an information recording surface thereof and pre-pits so pre-formatted as to deviate from the center of the track, a return beam of the irradiated beam is received by detectors split into two parts in a track direction to obtain a differential signal, the pre-pit is detected from this differential signal and control of recording and reproducing processings is executed by using the pre-pit detection signal so obtained as the reference.