1. An attribute determining method comprising: an image acquiring step of acquiring an image of a person to be determined; an attribute determination region detecting step of detecting at least two attribute determination regions selected from the group consisting of a head region, a facial region, and other regions from the image of a person to be determined; and an attribute determining step of determining an attribute based on images of the at least two attribute determination regions, wherein in the attribute determining step, an attribute is determined by combining the images of the at least two tribute determination regions, and in the combination of images, whether or not the at least two attribute determination regions belong to a same person is determined using an overlap degree of one of the attribute determination regions and an attribute determination region other than the one of the attribute determination regions.