PURPOSE: To inexpensively and uniformly initialize a whole disk in short time by permitting laser light to pass through an optical fiber, converging laser light in a condensing lens connected to the optical fiber and irradiating the recording film of the disk with light.

CONSTITUTION: Laser light emitted from a semiconductor laser 9 passes through the optical fiber 10 and it is converged in the beam of several hundred μm in the lens 11. The optical disk 1 is irradiated with the beam. A lens feed motor 13 can shift the lens 11 constant at linear speed in the direction of a radius as against the disk or constant at feed speed. The position of the lens 11 is detected and a control circuit 14 controls the revolving speed of the motor 12. When the opening number of the lens at that time is small, irregularity of initialization does not occur even if the focus direction of the condensing lens 11 is not servoed as against the recording film. Thus, the simple optical disk of high quality without irregularity can be initialized in short time.