WIRELESS POWER TRANSMISSION DEVICE AND WIRELESS POWER TRANSMISSION SYSTEM

A wireless power transmission device capable of reducing an output power of wireless power receiving device receiving power transmitted from a wireless power transmission device. The wireless power transmission device including: a DC (Direct Current)/DC converter; an inverter configured to convert output voltage of the DC/DC converter into AC voltage having driving frequency; a power transmission coil configured for the AC voltage to be supplied to from the inverter and configured to generate the AC magnetic field; a transmission-side resonance circuit including the power transmission coil; and control circuit configured to increase difference between a driving frequency of the inverter and a resonance frequency of the transmission-side resonance circuit when a predetermined condition is satisfied.