PURPOSE: To secure the exchangeability of an optical recording medium, by controlling a laser power by using an optical detector, and reading a bit of information in an identification information part, when the optical recording medium is loaded.

CONSTITUTION: A signal from the optical detector 26 is inputted to the identification circuit 31, and the signal is sent to a CPU32, then, the kind and the optimum reproducing, recording and erasing power of the optical recording medium are discriminated. And a requires signal is supplied to a laser driving circuit 34 through a D/A converter 33, and the reproducing, the recording and the erasure of the bit of information are performed by driving a laser beam 35 by an optimum power. Since it is necessary to change the laser power according to the radius position of the recording medium in a CAV system, the position is read by a position detector 36, and the bit of information for the position is supplied to the CPU 32, then, the laser beam is controlled so as to perform reproduction, recording, and erasure of the bit of information by the optical laser power corresponding to the radius position.