Abstract: A user authentication system uses an information code such as a two-dimensional information code. The authentication system includes an authentication device, and the user is authenticated by combining the authentication device with a user's mobile terminal. In the mobile terminal, an authentication code in which facial feature points extracted from user's facial images are recorded is stored in the memory. In the authentication device, facial feature points are extracted from images of a human's face captured by an imaging unit, after being determined to be in a facial recognizable state, and the authentication code is displayed on the screen of the mobile terminal. The e facial feature points recorded in the authentication code are read from the captured images of the authentication code. The extracted facial feature points and the read facial feature points are subject to matching with each other in order to authenticate the user.