To enable obtainment of a composite image including a movement trajectory of a moving body, even from a moving image including a background. Sampling means samples frames from moving image data. First mask frame calculating means calculates mask frames including mask regions, which correspond to positions of the moving body on the frames. Second mask frame calculating means accumulates and binarizes the mask frames to calculate a reference mask frame. Region cutout means masks the frames by using the mask frames and the reference mask frame to cut out moving body regions, which correspond to a moving body, from the frames. Composing means overwrites moving body regions on one of the frames in chronological order to obtain a composite image, which includes the movement trajectory of the moving body.