Optical disk apparatus and optical disk identifying method

In an optical disc drive capable of recording and playing back different kinds of optical discs, an actuator driving means brings an objective lens close to the optical disc, focus error signals are generated in front of and behind a position where leaser beam comes into focus on a signal surface of the optical disc, optical disc discriminating means discriminates a thickness of the optical disc from a difference in waveform of the focus error signal which is generated by focus deviation between leaser beam which passes through an outer periphery of the objective lens and leaser beam which passes through an inner periphery of the objective lens, and discriminates a kind of the optical disc from the thickness of the optical disc.