A portable electronic key device configured to wirelessly communicate with a lock side communication device to perform verification of an electronic key ID, the portable electronic key device comprising: a motion detector configured to detect movement of the portable electronic key device; a key function controller configured to monitor the movement of the portable electronic key device on the basis of a detection signal (Sac) of the motion detector and enable a predetermined function of the portable electronic key device to permit a predetermined operation when the movement is detected; a communication monitoring unit configured to monitor, when the predetermined function of the portable electronic key device is enabled, whether or not the portable electronic key device is receiving or capable of receiving a radio wave (Swk) regularly or irregularly transmitted from the lock side communication device; an operation controller configured to maintain the predetermined function of the portable electronic key device enabled in a period in which the movement of the portable electronic key device after start-up is not detected but the portable electronic key device is capable of receiving the radio wave (Swk), and a timer for measuring an elapsed time during which the movement of the portable electronic key device is not detected and during which the radio wave (Swk) is not received, wherein the operation controller disables the predetermined function of the portable electronic key device when a counting value of the timer becomes a threshold value (Ck) or more, characterized in that when the key function controller confirms that the movement is generated in the portable electronic key device, the timer is reset, and the communication monitoring unit is configured to determine whether or not the portable electronic key device has received the radio wave (Swk) while the portable electronic key device is in the start-up state, and when the communication monitoring unit determines that the portable electronic key device has received the radio wave (Swk) while the portable electronic key device is in the start-up state, the timer is reset. a motion detector configured to detect movement of the portable electronic key device; a key function controller configured to monitor the movement of the portable electronic key device on the basis of a detection signal (Sac) of the motion detector and enable a predetermined function of the portable electronic key device to permit a predetermined operation when the movement is detected; a communication monitoring unit configured to monitor, when the predetermined function of the portable electronic key device is enabled, whether or not the portable electronic key device is receiving or capable of receiving a radio wave (Swk) regularly or irregularly transmitted from the lock side communication device; an operation controller configured to maintain the predetermined function of the portable electronic key device enabled in a period in which the movement of the portable electronic key device after start-up is not detected but the portable electronic key device is capable of receiving the radio wave (Swk), and a timer for measuring an elapsed time during which the movement of the portable electronic key device is not detected and during which the radio wave (Swk) is not received, wherein the operation controller disables the predetermined function of the portable electronic key device when a counting value of the timer becomes a threshold value (Ck) or more, characterized in that when the key function controller confirms that the movement is generated in the portable electronic key device, the timer is reset, and the communication monitoring unit is configured to determine whether or not the portable electronic key device has received the radio wave (Swk) while the portable electronic key device is in the start-up state, and when the communication monitoring unit determines that the portable electronic key device has received the radio wave (Swk) while the portable electronic key device is in the start-up state, the timer is reset.