Apparatus and method for updating location information of idle mode mobile station in portable internet system

An apparatus and a method for updating location information according to movement of an idle mobile terminal in a mobile communication system are provided to reduce a load related to updating of location information of a mobile terminal and power consumption of the mobile terminal. A paging group registering unit(210) registers information of the first paging group in which a mobile terminal in an idle state is located. A mobile terminal location notifying unit(220) receives location information of the mobile terminal in the idle state and calculates movement speed of the mobile terminal. A time calculating unit(231) generates update-expectation time information and calculates a location information update-expectation time of the mobile terminal in the idle state. A timer operating unit(232) registers the calculated location information update-expectation time in a paging timer and operates the paging timer. When the operated paging timer expires, a location information updating unit(240) determines that the mobile terminal has been moved from the first paging group to the second paging group and updates the location information of the mobile terminal in the idle state.