A laser device configured to irradiate an object to be irradiated with laser light, LB, the laser device comprising: a laser light source configured to emit laser light, LB; a reference light source configured to emit reference light, RL; a swingable mirror that includes a first reflecting surface configured to reflect the laser light, LB, emitted from the laser light source in a direction different from a traveling direction to guide the laser light, LB, to the object to be irradiated and a second reflecting surface configured to reflect the reference light, RL, emitted from the reference light source in a direction different from a traveling direction, is configured as swingable to change an inclination angle of the first reflecting surface with respect to an optical path of the laser light, LB, incident on the first reflecting surface, and to change an inclination angle of the second reflecting surface with respect to an optical path of the reference light, RL, incident on the second reflecting surface when the inclination angle of the first reflecting surface with respect to the optical path of the laser light, LB, incident on the first reflecting surface changes; a reference light receiver configured to receive the reference light, RL, reflected by the second reflecting surface of the swingable mirror; a condensing lens that is disposed in an optical path of the laser light, LB, from the first reflecting surface of the swingable mirror toward the object to be irradiated and is configured to condense the laser light, LB; and characterized in that, the laser device further comprises: a controller configured to perform calibration processing, wherein, in the calibration processing, the controller is configured to make an observation of a state of the laser light, LB, incident on the object to be irradiated and an output of the reference light receiver while sequentially changing the inclination angle of the first reflecting surface of the swingable mirror with respect to the optical path of the laser light, LB, incident on the first reflecting surface of the swingable mirror, and is configured to update correspondence relationship information indicating a correspondence relationship between a target state of the laser light, LB, incident on the object to be irradiated and a target output of the reference light receiver based on a result of the observation. a laser light source configured to emit laser light, LB; a reference light source configured to emit reference light, RL; a swingable mirror that includes a first reflecting surface configured to reflect the laser light, LB, emitted from the laser light source in a direction different from a traveling direction to guide the laser light, LB, to the object to be irradiated and a second reflecting surface configured to reflect the reference light, RL, emitted from the reference light source in a direction different from a traveling direction, is configured as swingable to change an inclination angle of the first reflecting surface with respect to an optical path of the laser light, LB, incident on the first reflecting surface, and to change an inclination angle of the second reflecting surface with respect to an optical path of the reference light, RL, incident on the second reflecting surface when the inclination angle of the first reflecting surface with respect to the optical path of the laser light, LB, incident on the first reflecting surface changes; a reference light receiver configured to receive the reference light, RL, reflected by the second reflecting surface of the swingable mirror; a condensing lens that is disposed in an optical path of the laser light, LB, from the first reflecting surface of the swingable mirror toward the object to be irradiated and is configured to condense the laser light, LB; and a controller configured to perform calibration processing, wherein, in the calibration processing, the controller is configured to make an observation of a state of the laser light, LB, incident on the object to be irradiated and an output of the reference light receiver while sequentially changing the inclination angle of the first reflecting surface of the swingable mirror with respect to the optical path of the laser light, LB, incident on the first reflecting surface of the swingable mirror, and is configured to update correspondence relationship information indicating a correspondence relationship between a target state of the laser light, LB, incident on the object to be irradiated and a target output of the reference light receiver based on a result of the observation.