1. A foreign object determination device, comprising: an image acquisition unit for acquiring an image in which an authentication target to be subjected to fingerprint authentication has been captured; a region partitioning unit for partitioning the image acquired by the image acquisition unit into regions of mutually different colors by using predetermined determination criteria for determining differences in color; and a foreign object determination unit for determining whether a foreign object is included in the authentication target by using colors and/or areas of the regions partitioned by the region partitioning unit.