1. An image processing device that performs registration processing between a plurality of images using an image transformation defined by at least one inter-frame motion vector, comprising: a lens characteristic acquisition unit for obtaining a lens characteristic of an imaging lens that photographs the plurality of images; a motion vector measurement region setting unit for setting, on the basis of the lens characteristic, a plurality of motion vector measurement regions in each of which a motion vector is to be measured; a motion vector calculation unit for calculating the motion vectors of the plurality of motion vector measurement regions; a motion vector reliability calculation unit for calculating a reliability of each of the calculated motion vectors; and a motion vector integration processing unit for calculating the at least one inter-frame motion vector by integrating the motion vectors of the plurality of motion vector measurement regions in accordance with the reliability of the motion vectors.