A motion detecting includes a fetcher which repeatedly fetches an object scene image having a designated resolution. An assigner assigns a plurality of areas each of which has a representative point to the object scene image in a manner to have an overlapping amount different depending on a size of the designated resolution. A divider divides each of a plurality of images respectively corresponding to the plurality of areas assigned by the assigner, into a plurality of partial images, by using the representative points as a base point. A detector detects a difference in brightness between a pixel corresponding to the representative point and surrounding pixels, from each of the plurality of partial images divided by the divider. A creator creates motion information indicating a motion of the object scene image fetched by the fetcher, based on a detection result of the detector.