A beam irradiation apparatus includes: an optical element which changes a travel direction of a laser beam by being rotated in a predetermined direction; an actuator which rotates the optical element in the direction; a refractive element which is disposed in the actuator and rotates in association with rotation of the optical element; a servo beam source which emits a servo beam to the refractive element; a photodetector which receives the servo beam refracted by the refractive element and outputs a signal according to a position where the servo beam is received; and a power adjustment circuit which adjusts emission power of the servo beam source. The power adjustment circuit adjusts the emission power so that a reception amount of the servo beam in the photodetector becomes constant based on an output signal from the photodetector.