1. An image processing apparatus, comprising: an image acquisition device which acquires a first image and a second image; a feature point extraction device which extracts a plurality of feature points from the first image; a corresponding point detection device which detects a plurality of corresponding points by tracking, in the second image, a plurality of points in the second image respectively corresponding to the plurality of feature points extracted from the first image; an image transformation parameter calculation device which calculates an image transformation parameter for matching the first image and the second image with each other among the detected plurality of corresponding points; an image transformation device which transforms the second image using the calculated image transformation parameter and acquires the transformed image as a third image; and a feature point existing region determination device which determines whether or not the feature point extracted from the first image is positioned in an invalid image region at an edge of the image, the invalid image region being generated by execution of a predetermined filtering process on the first image, wherein the corresponding point detection device, when it is determined that the feature point extracted from the first image is positioned in the invalid image region, tracks the determined feature point using the first image and the third image.