A method for biometric authentication based on face recognition, the method includes changing a first processor to an active state to try a detection of face area of a subject for a preset time period with respect to image information of the subject that is successively acquired; changing the second processor to an idle state when the face area is not detected for the preset time period and allowing a second processor in an active state to try a detection of face area; and returning the first processor to the active state and resuming biometric authentication using the detected face area when the face area is detected by the second processor.