Provided is an electronic key system capable of providing an instruction to an automobile through a portable device having biometric authentication of a user. When biometric information of a wearer is detected by a biometric recognition sensor (2), a portable device (1) worn on a user determines with a biometric authentication unit (8) whether or not the detected biometric information is matched with biometric information of a previously-registered user. When the biometric authentication unit (8) authorizes that the wearer is a registered user, the portable device (1) enables, through a communication control unit (9), near-distance wireless communication with a control unit (15) mounted on an automobile (16) through a wireless communication device (6). Thus, the portable device (1) can provide an operational instruction to the automobile (16) through wireless communication with the control unit (15).
