PURPOSE: To attain the effective movement of an image with small eccentricity by arranging a moving optical element satisfying a specific condition between the horizontal magnification of a moving optical element and the magnification of an optical element on the image side.

CONSTITUTION: When it is defined that the horizontal magnification of the moving element is βa and the magnification of the optical element on the image side is βb (provided that when no optical element exists on the image side, βb=1), βb(1-βa)≥1 is satisfied. An image forming lens system consists of a 1st focal lens 5, a 2nd lens group 6 and a 3rd lens group 7 in order and each lens group consists of one or plural lenses. The 2nd lens group 6 is supported by a supporting device so that parallel eccentricity can be optionally attained in the direction vertical to the optical axis of the image forming lens system and is enabled to be two-dimensionally driven by an actuator 3 such as a piezoelectric element. Since a purpose can be attained only by the short movement of the moving part, a space for the movement can be reduced, the whole device can be miniaturized and accurate follow-up to the moving part can be attained also at a high frequency level or a large amplitude value because the moving distance is small.