PURPOSE: To attain the focusing and tracking controls of light beams regardless of the length of record and erasion by shifting the center part of the light beam to the edge part of an erased part together with microvibrations given to the center part in case the erased part is long and discontinuous.

CONSTITUTION: The reflected light is not produced any more when a pickup 1 of an optical system reaches a record erased part 11, and therefore a read amplifier 2 has no output. A no-signal detecting circuit 4 detects said no-output state and delivers a signal to an FF circuit 5. Receiving this signal, the circuit 5 gives an indication to a tracking control circuit 8 for offset of the optical axis of a light beam and at the same time delivers a signal to an FF circuit 6. Then the circuit 6 delivers a wobbling indication signal of the light beam to a wobbling control circuit 9. As a result, the center of the optical axis is shifted to a position 13 from a position 12 and the wobbling control is carried out. The light beam is reset to its original state when the pickup 1 reads the information again.