A first current generator circuit generates a first current having a current value variable in accordance with a first control signal. A second current generator circuit generates a second current by limiting the first current so as to have a current value variable in accordance with a second control signal. A third current generator circuit generates a third current by limiting the second current so as to have a current value variable in accordance with a third control signal, and supplies the third current to the semiconductor laser element. Rates at which the first and second control signals change are set to be lower than a rate at which the third control signal changes.