To provide a laser oscillation device capable of realizing accurate irradiation reproducibility of laser light without using a large-sized expensive voltage detection part with complicated circuit constitution.

The device is equipped with a 1st rectification part 2 which converts the AC voltage of a three-phase AC power source 1 into a DC voltage, a current limiting part 3 which limits the current when the power source is turned on, a path switching part 4 which is provided in parallel to the current limiting part 3, a laser resonance part which converts the DC voltage of the 1st shaping part 2 into laser light, a 2nd rectification part 11 which rectifies a three-phase AC voltage, a voltage detection part 12 which detects the DC voltage outputted by the 2nd rectification part 11, and an integration part 13 which integrates the output signal of the voltage detection part 12. By short-circuiting the path switching part 4 when the integration part 13 detects the AC voltage from the three-phase AC power source 1 to improve response and detection precision of detection, the accurate irradiation reproducibility of laser light can be realized.