Lh indicates the amount of image-surface movement of a photographic subject; Ls, a scan driving range; Lps, a scan driving range required to detect a peak; Li, the amount of initial position driving. Based on the speed of a photographic subject (inclination of a photographic-subject movement amount profile H), a body controlling unit sets Li as a driving amount and a driving direction of initial position driving in such a manner as to satisfy Lh