1. An image processing device comprising: a first difference detection unit which detects difference information of a first image of first and second frames shot with a first shooting condition; a second difference detection unit which detects difference information of a second image of the first and second frames shot with a second shooting condition; and a combining unit which combines the difference information of the first image detected by the first difference detection unit and the difference information of the second image detected by the second difference detection unit on the basis of the first or second image and generates a motion vector of the first frame on the basis of the combined difference information.