1. An image processor comprising: a similar-image detecting part configured to detect a similar image region in each of a plurality of frame images captured by rolling shutter type exposure, said similar image region being similar among said plurality of frame images; a displacement-vector detecting part configured to detect a displacement vector of said similar image region with respect to a common reference position among said plurality of frame images; an average calculating part configured to calculate an average of displacement vectors in said plurality of frame images; and a correcting part configured to shift said similar image region in one of said plurality of frame images such that said displacement vector of said similar image region becomes said average.