A face authentication device is provided that can perform personal identification with high accuracy regardless of an imaging environment for an input face image. The face authentication device comprises: a first similarity calculation unit (50) for calculating a similarity between a feature data item of an input face image data item and a feature data item of a face image data item registered in a face image data registration unit (30); a second similarity calculation unit (70) for calculating similarities between feature data items stored in a feature data storage (60) and the feature data item extracted by a first feature extraction unit (20); a threshold setting unit (80) for, based on the similarities calculated by the second calculation unit (70), setting a threshold for judging whether the input face image data item and the registered face image data item are of an identical person or not; and an identity determination unit (90) for determining whether the input face image data item and the registered face image data item are data items of an identical person or not by comparing the threshold set by the threshold setting unit (80) and the similarity calculated by the first similarity calculation unit (50).