ELECTRIC POWER TRANSMISSION DEVICE, ELECTRIC POWER TRANSMISSION ANTENNA DEVICE, AND WIRELESS ELECTRIC POWER SUPPLY SYSTEM

An electric power transmission device includes: an oscillator that outputs an AC signal; a controller that outputs a control signal; and a modulator that modulates an AC signal output from the oscillator in response to the control signal. The control signal is a signal for selecting an antenna that radiates the AC signal from among a plurality of antennas.