Disclosed herein is a user authentication apparatus that captures images of the back and/or the palm of a hand using both a mobile camera, such as a smart phone or a smart pad, and a high-resolution stationary camera embedded in a PC, extracts various types of biometric information from the captured images, registers the extracted biometric information, and authenticates a new image when the new image is input. The user authentication apparatus includes a hand area detection unit for detecting a hand area from an input hand image, a hand area normalization unit for binarizing the detected hand area and normalizing the binarized hand area, a hand biometric information extraction unit for extracting unique hand biometric information from the normalized hand area, and a hand biometric information registration and authentication unit for registering the hand biometric information and authenticating the corresponding user based on the hand biometric information.