In a mobile communication system, a mobile-station location information management device creates plural transmission-power output data-sets including individual pieces of transmission-power data of plural base-stations with changing the transmission-power of the plural base-stations; creates plural reception-power data-tables individually corresponding to the created plural transmission-power output data-sets and each including plural pieces of divided-area data individually corresponding to plural individual divided-areas within a location-detection target area where each piece of divided-area data includes reception-power data of signals transmitted from the plural base-stations; selects a reception-power data table corresponding to the changed transmission-power data-set from among the created plural reception-power data-tables when the transmission-power of the plural base-stations are changed after the mobile-station has moved into the location-detection target area; and detects, as a location of the mobile-station, an area indicated by divided-area data where a difference from a reception-power data-set received from the mobile-station is slight, within the selected reception-power data-table.