An extraction unit (21) treats two or more consecutive frames of a plurality of frames constituting video data as a time-window frame, and extracts a plurality of time-window frames from the video data so as to cause at least one frame to be overlappingly included in adjacent time-window frames. A tracking unit (22) treats each time-window frame as a target time-window frame, and tracks target objects in the target time-window frame to generate a tracking result. An integration unit (23) integrates tracking results generated in individual time-window frames, based on a frame overlappingly included in more than one time-window frame, to generate an integration result.