WIRELESS POWER TRANSMISSION SYSTEM

There is provided a frequency controller apparatus for use in a wireless power transmitter apparatus configured to wirelessly transmit an inputted power from a power transmitting antenna that includes a first resonant circuit, toward a power receiving antenna that includes a second resonant circuit and is electromagnetically coupled to the power transmitting antenna at a predetermined transmission frequency. The frequency controller apparatus includes controller means for changing the transmission frequency during a power transfer, and the controller means sets a decrease amount when decreasing the transmission frequency, so that the decrease amount is smaller than an increase amount when the transmission frequency is increased.