A biometric-electronic key system comprising: - an electronic key that is configured to store an electronic key ID; - a vehicle comprising a verification ECU that is capable of wirelessly communicating with the electronic key and of performing: (i) an interior key verification that verifies the electronic key ID through communication within a passenger compartment and (ii) a biometric authentication that authenticates biometric information of a user, wherein the verification ECU is configured to permit starting of an engine of the vehicle when an engine switch is operated when the interior key verification and the biometric authentication have both been accomplished; the verification ECU also comprising: - a non-accomplishment notification unit that is configured to present the user with a non-accomplishment notification of the biometric authentication when the biometric authentication cannot be accomplished; - a key operation authentication unit that is configured to execute an alternative authentication corresponding to an electronic key operation performed by the user instead of the biometric authentication in response to the non-accomplishment notification; and - an actuation permission unit that is configured to permit the actuation of the engine of the vehicle when the biometric authentication cannot be accomplished as long as the alternative authentication performed by the key operation authentication unit has been accomplished; wherein: - the alternative authentication corresponding to the electronic key operation includes an immobilizer authentication of the electronic key or a motion operation authentication of the electronic key; - the immobilizer authentication of the electronic key corresponds to the verification of the electronic key ID through near-field wireless communication; - the motion operation authentication of the electronic key corresponds to the detection of a specified pre-registered motion of the electronic key; the biometric-electronic key system also comprising that: - the engine switch includes a button on which a sensor is arranged to detect the biometric information (Dbi) of the user; - the engine switch incorporates an immobilizer antenna to perform the immobilizer authentication; - the electronic key incorporates a motion detector to perform the motion operation authentication; - when the user presses the button of the engine switch, the biometric authentication is executed to verify the biometric information (Dbi) detected by the sensor; and - the actuation permission unit is configured to permit the engine of the vehicle to be started when the biometric authentication cannot be accomplished as long as the alternative authentication performed by the key operation authentication unit has been accomplished. - an electronic key that is configured to store an electronic key ID; - a vehicle comprising a verification ECU that is capable of wirelessly communicating with the electronic key and of performing: (i) an interior key verification that verifies the electronic key ID through communication within a passenger compartment and (ii) a biometric authentication that authenticates biometric information of a user, wherein the verification ECU is configured to permit starting of an engine of the vehicle when an engine switch is operated when the interior key verification and the biometric authentication have both been accomplished; - a non-accomplishment notification unit that is configured to present the user with a non-accomplishment notification of the biometric authentication when the biometric authentication cannot be accomplished; - a key operation authentication unit that is configured to execute an alternative authentication corresponding to an electronic key operation performed by the user instead of the biometric authentication in response to the non-accomplishment notification; and - an actuation permission unit that is configured to permit the actuation of the engine of the vehicle when the biometric authentication cannot be accomplished as long as the alternative authentication performed by the key operation authentication unit has been accomplished; - the alternative authentication corresponding to the electronic key operation includes an immobilizer authentication of the electronic key or a motion operation authentication of the electronic key; - the immobilizer authentication of the electronic key corresponds to the verification of the electronic key ID through near-field wireless communication; - the motion operation authentication of the electronic key corresponds to the detection of a specified pre-registered motion of the electronic key; - the engine switch includes a button on which a sensor is arranged to detect the biometric information (Dbi) of the user; - the engine switch incorporates an immobilizer antenna to perform the immobilizer authentication; - the electronic key incorporates a motion detector to perform the motion operation authentication; - when the user presses the button of the engine switch, the biometric authentication is executed to verify the biometric information (Dbi) detected by the sensor; and - the actuation permission unit is configured to permit the engine of the vehicle to be started when the biometric authentication cannot be accomplished as long as the alternative authentication performed by the key operation authentication unit has been accomplished.