A mirror driver drives deflection mirror surfaces into a pivoting action at a frequency belonging to a first drive frequency band in which the high-frequency side of a first resonance frequency band partially overlaps the low-frequency side of a second resonance frequency band, so that the deflection mirror surfaces deflect a light beam. Hence, the deflection angles of light beams change, while canceling out each other the changes of the deflection angles of the light beams deflected by the deflection mirror surfaces owing to changes of resonance characteristics. Because of this, even when the resonance characteristics change, it is possible to stabilize the deflection angle of the light beam deflected by the first deflection mirror surface and further deflected by the second deflection mirror surface.