An apparatus for determining a fake image includes an image-acquiring block for acquiring an image captured by and input from a camera; and a background-learning block for learning a background of the image to create a learning background. Further, the apparatus for determining the fake image includes a face extracting-block for extracting a face region of a person to be authenticated when an input image for authentication is transmitted from the camera; and an inter-background comparing block for comparing a present background of an input image with the learning background. Furthermore, the apparatus for determining the fake image includes a motion information-comparing block for extracting motion information in the face region and the present background to compare the same with each other; and a fake image-determining block for determining whether the input image is faked using the compared results of the motion information and the backgrounds.