A beam irradiation apparatus includes: an actuator which scans a target region with a laser beam; a photodetector which receives a servo beam and outputs a signal according to a beam reception position; an optical unit which makes the servo beam displaced on the photodetector in association with driving of the actuator; and a position signal generation circuit that generates a signal according to the reception position of the servo beam based on an output signal from the photodetector. The position signal generation circuit has a signal removal circuit that removes a disturbance signal generated when the laser beam is incident on the photodetector, from an output signal of the photodetector.