In a mobile station, a period for receiving a GPS signal from a predetermined satellite based on data for satellite reception is set up by a timer, and the GPS signal whose reception level is higher than a threshold value is awaited. Until elapsed time reaches a preset time, indoor counter is incremented if the GPS signal is unable to be received or outdoor counter is incremented if the GPS signal is able to be received. When each counter reaches a specified value, each mode is determined. If the mode is different from a previous mode, a mode shift is executed and setups of user interfaces, display, speaker and others, are altered for the updated mode, indoor or outdoor.