PURPOSE: To easily adjust the optical axes of a semiconductor laser and lens in a short time by connecting a monitor to an enlarging device which is positioned on the opposite side of the laser with respect to the lens while the optical axis of the enlarging device is aligned with that of the laser and two- dimensionally observing the output end face of the laser through the lens.

CONSTITUTION: By two-dimensionally observing the output end face of a semiconductor laser 1 by using an enlarging device 2 and monitor 5 in a state where a lens 4 is not mounted, the light emitting point of the laser 1 is aligned with the optical axis of the device 2. After interposing the lens 4 between the laser 1 and device 1, the lens 4 is again focused by moving the device 2 or laser 2 along their optical axes so that the output end face of the laser 1 can be observed. Then the optical axis of the light emitting point is aligned with that of the lens 4 by again observing the output end face of the laser 1 through the lens 4 and moving the lens 4 in a plane perpendicular to the optical axis of the lens 4 by means of a fine adjustment table 3.