PURPOSE: To provide a light beam scanning device capable of preventing large loads from being added to the scanning means of a galvanometer mirror or the like.

CONSTITUTION: As shown in (A), a level drastically rises from a standard level at a point P3, the ascending degree of the level becomes moderate around the level V1, the level V1 is attained, the state is held for a prescribed time, the level drastically falls for a prescribed level thereafter and then, the level lowers to the level V2 with a prescribed inclination. The level drastically rises from the level V2 at the point P2, the descending degree of the level becomes moderate around the standard level, the standard level is attained and the galvanometer mirror is driven by the driving signal L3 of a waveform held for the prescribed time at the standard level. Thus, the inclination of the fluctuation of a rotating speed at the time of drastically rotating and stopping the mirror is below a prescribed value.