1. A motion vector searching apparatus to which a reference image, an object image and a weight parameter for the reference image are inputted, for searching a motion vector based thereon, the apparatus comprising: an inverse weighting section for generating an inverse weighted object image by performing, on the object image using the weight parameter, a weighting inverse from a weighting performed on the reference image using the weight parameter; an image comparing section that compares the generated inverse weighted object image with the reference image to obtain a comparison value indicating a degree of approximation between the two images; and a determination section that determines an optimum motion vector by utilizing the comparison value, wherein the comparison value obtained by the image comparing section is either one of: (a) a value obtained by summing, for all of the pixels of the inverse weighted object image, an absolute value of a difference of pixel values at the same pixel position in the inverse weighted object image and the reference image, and (b) a value obtained by summing, for all of the pixels of the inverse weighted object image, a square of the difference of pixel values at the same pixel position in the inverse weighted object image and the reference image.