A radio transmitter includes a radio module, a battery from which power is fed to the radio module, and a metal plate. The radio module includes a transmission module generating a transmission signal and an antenna configured to wirelessly transmit the transmission signal. The metal plate is located so as to cover a part of the battery and a part of the antenna. The battery is electromagnetically coupled to the antenna. A main radiation direction of the antenna is parallel to a principal surface of the metal plate.