1. An object detection apparatus, comprising: a processing object region determination unit configured to set a symmetry axis in an image region included in an image and divide said image region into a determination image region and a reference image region so as to be line symmetric with respect to said symmetry axis; a variance acquisition unit configured to acquire a degree of variance of image feature amount in said image region; a matching determination unit configured to acquire a matching value between said determination image region and said reference image region and determine the symmetry between said determination image region and said reference image region with respect to said symmetry axis on the basis of a corrected matching value obtained by correcting said acquired matching value in accordance with said degree of variance; and an object region detection unit configured to detect an image region which is line symmetric with respect to said symmetry axis on the basis of a determination result obtained by said matching determination unit.