A shutter speed determination device includes a motion detector and controller. The motion detector, on a block-by-block basis having a specified block size, performs detection processing of a motion vector for image data obtained by capturing a subject image. The controller, while reducing the block size, causes the motion detector to execute the detection processing repeatedly, each time executing the detection processing the controller finds a motion vector related value that changes in a same direction as a direction in which a magnitude of the motion vector changes, the controller determines a shutter speed used when capturing the subject image thereafter, based on the motion vector related value found.