1. An apparatus for analyzing a correlation between images, comprising: a feature data generation unit for determining feature points of each image, and generating feature data including pieces of feature point orientation information for the respective feature points; and a relation analysis unit for analyzing a correlation between an image and another image using the feature data generated by the feature data generation unit, wherein the relation analysis unit comprises: a corresponding feature point determination unit for determining pairs of corresponding feature points between the images to be compared using the feature data generated by the feature data generation unit; and a reliability estimation unit for estimating reliability of analysis of a correlation between the images, based on the feature point orientation information of the feature points included in the feature point pairs determined by the corresponding feature point determination unit, wherein the reliability estimation unit estimates the reliability of the analysis of the relation between the images, based on a probability density function for estimated values of differences between orientations of the feature points included in the respective feature point pairs.