Erroneous data erasure owing to radiation of laser beam with excessive power to the recording layer of the multilayered optical disc upon servo-off while reproducing data of the disc is prevented. When detecting the servo-off based on the amplitude of the tracking error signal or the focus error signal, the laser beam power is reduced to a predetermined minimum value, and the laser beam power value is set again based on the address of the recording medium, which has been obtained later for reproduction. The laser beam power value is changed by applying an offset to the drive current or changing the target value under APC.