A laser output power command determination value from a controller (17) is input to an upper limit current determination unit (32), and an upper limit current value to be decided based on the laser output power command determination value is determined. Then, a second comparator (30) compares a command current value determined from the laser output power command determination value and a laser output power command determination value measured with a power monitor (13), with an upper limit current value determined with a upper limit current determination unit (32). The second comparator (30) determines a command current value when the upper limit current value is greater than the command current value and the upper limit current value when the command current value is greater than the upper limit current value, as a reference current value, by which reference current value a current to be supplied to pumping means is configured to be controlled. In such a configuration, an upper limit current value is determined according to a laser output power command determination value, whereby an increased current to be supplied to the pumping means, i.e., the increase of energy to be supplied to a laser oscillator apparatus is avoided, and an energy loss in the optical component is reduced, which prevents damage development from leading to the replacement of the component.