he The target includes a plurality of keypoints of a body including a plurality of joints and the 3D position of the target is identified by positions of the plurality of keypoints. A bounding box and reference 2D joint position determining unit determines a bounding box surrounding the target in a camera image at a target frame to be predicted subsequent to at least one frame at which imaging is performed by the plurality of cameras using the 3D positions of the keypoints of the target at the at least one frame and acquires reference 2D positions of the keypoints projected from the 3D positions of the keypoints of the target onto a predetermined plane. A 3D pose acquiring unit acquires the 3D positions of the keypoints of the target at the target frame using image information in the bounding box and the reference 2D positions.