PURPOSE: To stabilize the optical output of a semiconductor laser element with a simple circuit, by controlling each driving current according to the emission light of any one of semiconductor laser elements.

CONSTITUTION: A photodiode 2 receives the optical output of an element out of semiconductor elements 11, 12,..., 1n constitution an integrated type semiconductor laser array 1, and converts it into a photo current. A current-voltage conversion part 3 converts the photo current into a voltage, and generates a signal showing the optical output level of the semiconductor laser element 11. A voltage distribution part 4 distributes the optical output level signal to the respective semiconductor laser elements 11, 12,..., 1n. In a driving signal setting part 5, each of the driving signal setting unit 51, 52,Sv, 5n generates in accordance with a distributed voltage a control signal for setting a driving current for each semiconductor laser element. Corresponding with the control signal, driving circuits 61, 62,..., 6n generate the respective driving currents, and drive a plurality of the corresponding semiconductor laser elements.