A power transmission device includes an inverter using a frequency f11 lower than a frequency f0 between a first resonator and a second resonator or a frequency f12 higher than the frequency f0 to generate a first power; an oscillator using a frequency f10 lower than a frequency fr between the first resonator and the second resonator or a frequency f20 higher than the frequency fr to generate a second power; and a power transmission control circuitry setting a foreign object detection period between first and second transmission periods, using the frequency f11 or frequency f12 in the first transmission period, using the frequency f10 or frequency f20 in the foreign object detection period, and if it is determined that a substance is present in the foreign object detection period, transmitting power in the second transmission period at a frequency different from the frequency used in the first transmission period.