1. A depth measurement apparatus for calculating depth information of a subject in an image by using a plurality of images including a first image and a second image, the apparatus comprising: a region segmentation unit configured to segment at least one of the images into regions based on an image feature amount, wherein, in each of the regions, pixels are presumed to be substantially equal in depth to the subject; and a depth calculation unit configured to calculate a depth for each region resulting from the segmentation by the region segmentation unit and serving as a processing target region for depth calculation, to set the calculated depth as the depth of the processing target region, wherein the depth calculation unit is further configured to calculate the depth based on data in a processing target region of the first image and data in a processing target region of the second image.