PURPOSE: To enable the stable execution of scanning without generating unequalness in scanning pitch by a light beam even when a fluctuation arises in a resonance frequency by detecting the vibration state of a reflection mirror of a resonance type optical deflector, forming a reference signal in synchronization with or proportion to this vibration state signal and controlling the sub- scanning and transporting speed of an object to be scanned in synchronization or proportion to the reference signal.

CONSTITUTION: The resonance type optical deflector 78 resonates and vibrates the reflection mirror 16 in accordance with the driving power supplied from a driving coil constituting a deflector driving circuit 34. The feedback signal of the driving signal supplied to the coil is supplied to a vibration state detecting circuit 36. The vibration state signal of the reflection mirror 16 detected by this vibration state detecting circuit 36 is supplied to a reference signal forming circuit 38 by which the reference signal is formed. The reference signal is supplied to a motor rotating speed control circuit 40. This motor rotating speed control circuit 40 controls driving of a sub-scanning and transporting motor 28 in accordance with the reference signal.