A mobile phone has an upper antenna at the top of a casing constituting a body and a lower antenna at the bottom of the casing. The mobile phone includes an influence-on-antenna evaluation unit for evaluating the influence of the ambient environment on each of the antennas by determining an input impedance (Z) of each antenna at predetermined time intervals during connection and by comparing the determined input impedance with a predetermined input-impedance reference value (Z0). Transmission power corresponding to the amount of radio waves radiated is supplied to the antenna that is less affected by the ambient environment and transmission power is not supplied to the antenna that is more affected by the ambient environment.