PURPOSE: To reduce the electric power to be controlled and thus to realize a miniature and economical laser device by dividing the DC power source into the DC power source featuring nearly the constant output voltage and the DC power source featuring the variable output voltage respectively.

CONSTITUTION: The DC power source is divided into DC power source 11 featuring nearly the constant and basic output voltage and DC power source 3 featuring variable output voltage in a small range respectively. Thus, the capacity of power source 3 is reduced with a small ripple content ratio secured for the DC voltage. Accordingly, the capacity of the smoothing circuit can be decreased with the output voltage lowered for both power source 11 and 3. As a result, a low level of the reverse dielectric strength suffices for the rectifying diode, thus realizing the miniature and economical power source and the laser device as a whole.