1. A medical imaging system, comprising: an image generating unit which captures an image of a subject and generates a medical image which is a still image; a region extracting unit which extracts a subject region from the medical image and extracts a local region which includes no edge from the subject region; a motion judging unit which extracts high spatial frequency components from the local region extracted by the region extracting unit and judges whether there is any motion in the subject during image capture based on the extracted high spatial frequency components; and a controlling unit which causes an outputting unit to output a judgment result made by the motion judging unit.