A laser apparatus includes a laser medium; a light source that radiates light to the laser medium, thereby exciting the laser medium and raising the temperature thereof; a reflecting unit having a first plane that reflects light within a predetermined wavelength range from light generated by excitation of the laser medium; and an output mirror disposed opposite the reflecting unit, with the laser medium being interposed therebetween, and causing laser oscillation by inducing resonance of the light within a predetermined wavelength range between the first plane and the output mirror. The reflecting unit is configured to be movable between a position in which light resonance is induced between the output mirror and the first plane and the laser apparatus is set to an oscillation state and a position in which the laser apparatus is set to a non-oscillation state.