In a mobile telephone system including a mobile telephone base station (20) connected to a telephone network (40) and a mobile telephone apparatus (10) which includes a first GPS unit for receiving a GPS wave as a first received GPS signal to obtain position data of the mobile telephone apparatus by information processing with reference to the first received GPS signal and a radio section for transmitting, by radio communication, the position data of the mobile telephone apparatus to the mobile telephone base station to make the mobile telephone base station inform the telephone network of the position data of the mobile telephone apparatus, the mobile telephone base station includes a mobile telephone base section for transmitting, by radio communication, position information of the mobile telephone base station to the mobile telephone apparatus to enable the mobile telephone apparatus to use the position information of the mobile telephone base station instead of the position data of the mobile telephone apparatus. Preferably, the mobile telephone base station further includes a second GPS unit for receiving the GPS wave as a second received GPS signal to obtain the position information of the mobile telephone base station by information processing with reference to the second received GPS signal. The mobile telephone base section is connected to the second GPS unit to be supplied with the position information of the mobile telephone base station from the second GPS unit.