An authentication device including: a processor; a first communication section installed at a vehicle and configured to perform first wireless communication with a terminal; and a plurality of second communication sections installed at the vehicle and configured to perform second wireless communication with the terminal, the processor being configured to: compute a distance and an angle of a position of the terminal with respect to the first communication section based on the first wireless communication of the first communication section with the terminal; cause a second communication section that, out of the plurality of second communication sections, corresponds to the computed angle, to execute the second wireless communication with the terminal; and determine, based on the executed second wireless communication and the computed distance, whether or not the terminal is present in an area corresponding to the second communication section executing the second wireless communication.