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, a portable device worn on a user determines with a biometric authentication unit whether or not the detected biometric information is matched with biometric information of a previously-registered user. When the biometric authentication unit authorizes that the wearer is a registered user, the portable device enables, through a communication control unit, near-distance wireless communication with a control unit mounted on an automobile through a wireless communication device. Thus, the portable device can provide an operational instruction to the automobile through wireless communication with the control unit.
