There was the problem that the pressure of the laser medium rises from the target value by the heat when generating laser light. The laser oscillator includes a controller, laser medium flow path, resonator part, blower, pressure detecting part, laser medium supply-exhaust part, and temporary stop command part. The controller controls the resonator part to stop to generate laser light if a temporary stop is commanded, controls the blower 18 to slow the rotational speed of the blower from the first rotational speed to the second rotational speed, and controls the laser medium supply-exhaust part so that the pressure is the second target value lower than the pressure at the time when the rotational speed of the blower is the second rotational speed.