1. A non-transitory computer-readable medium storing a program for tracking a feature point in an image that causes a computer to execute a process, the process comprising: calculating first values indicating degree of corner for respective pixels in another image, based on change of brightness values in horizontal direction and vertical direction; calculating second values indicating degree of similarity between respective areas in the another image and a reference area around the feature point in the image, based on comparison between the respective areas and the reference area; calculating third values indicating overall degree of corner and similarity, based on the first values and the second values; and tracking the feature point by identifying a point in the another image corresponding to the feature point in the image, based on the third values.