1. A people counting device comprising: an image acquisition unit configured to acquire an image from an imaging device; a head coordinate detection unit configured to detect a head coordinate of a target person from the image; a foot coordinate estimation unit configured to estimate a foot coordinate of the target person from the detected head coordinate; an individual region detection unit configured to perform region segmentation of the image and to give an attribute to each of regions; a foot coordinate correction unit configured to determine whether the target person overlaps another person based on the given attribute and to correct the foot coordinate of the target person estimated by the foot coordinate estimation unit when the persons are determined to overlap each other; a foot coordinate region inside/outside determination unit configured to determine whether the foot coordinate exists in a detection region set in the image; and a people counting unit configured to count foot coordinates determined to exist in the detection region by the foot coordinate region inside/outside determination unit.