1. An image processing device, comprising: a three-dimensional image data input unit which enters three-dimensional image data representing a three-dimensional image; a subject extraction unit which extracts a subject from the three-dimensional image data; a spatial vector calculating unit which calculates a spatial vector of the subject from a plurality of planar image data having different viewpoints contained in the three-dimensional image data; and a three-dimensional image data recording unit which records the spatial vector and the three-dimensional image data in association with each other.