1. A face image recognition apparatus comprising: a memory in which a reference feature amount of a face of a to-be-recognized person is previously registered, an image input section which inputs a face image of a person, a feature amount extracting section which extracts a feature amount of a face based on the face image input by said image input section, a recognition section which determines a recognition rate between the feature amount extracted by said feature amount extracting section and the reference feature amount registered in said memory, and a feature amount adding section which additionally registers the feature amount extracted by said feature amount extracting section as a new reference feature amount into said memory when the recognition rate determined by said recognition section is lower than a preset value.