A laser oscillation device can prevent a laser medium-circulating pipe from expanding. The laser oscillation device includes a resonator part, which has an introduction port, through which a laser medium is introduced, and a discharge port, from which the laser medium is discharged, and which generates a laser beam, a laser medium-circulating pipe having one end connected to the introduction port, and the other end connected to the discharge port, a blower arranged in the laser medium-circulating pipe, to circulate the laser medium so that the laser medium is introduced from the introduction port to the resonator part, and the laser medium introduced to the resonator part is discharged from the discharge port, and a heat-insulating mechanism which is provided in the laser medium-circulating pipe, to block heat conduction between the laser medium flowing through the laser medium-circulating pipe and the laser medium-circulating pipe.