Disclosed is a method of managing an allocated address through a coordinator in a Low Power Wireless Personal Area Network (LoWPAN) including receiving a first beacon data request message from a mobile node that has entered into a communication region of the coordinator; measuring a Link Quality Indication (LQI) of the first beacon data request message, setting the measured LQI as a minimum communication threshold value with the mobile node, and setting an alarm region that is an LQI range for sensing whether the mobile node leaves the communication region; if a second beacon data request message is received from the mobile node, measuring an LQI of the second beacon data request message, and checking whether the measured LQI of the second beacon data request message is included in the alarm region; and if the LQI is included in the alarm region, periodically transmitting a node alive check message to the mobile node.