To realize the derivation of high-density parallax information by using an inexpensive calculator of low processing capacity.

An image processor 120 comprises: a data holding unit 152 configured to hold parallax information indicating one or more parallaxes obtained in the past from the present; an image acquiring unit 150 configured to acquire two image data imaged by using corresponding optical axes different from each other; a search range determination unit 160 configured such that a search range of a partial image corresponding to one of the two image data, which corresponds to a reference partial image at an arbitrary image position of the other predetermined image data of the two image data is determined based on a parallax indicated by the parallax information in the past held in association with the arbitrary image position; a partial image search unit 162 configured to search for the corresponding partial image from the search range of the determined one image data; and a parallax derivation unit 164 configured such that a parallax is derived from the arbitrary image position and the image position of the searched corresponding partial image, and the parallax information indicating the parallax is held in the data holding unit in association with the arbitrary image position.