A wireless power transmission device includes a contactless transmitter unit, a contactless receiver unit and a step-down transformer. The transmitter unit receives an input AC power. A receiver coil of the receiver unit and a transmitter coil of the transmitter coil are electromagnetically coupled with each other. The input AC power is electromagnetically coupled to the receiver coil through the transmitter coil. Consequently, the input AC power is converted into a first output AC power. A first coil and a second coil of the step-down transformer are electromagnetically coupled with each other. The first coil is electrically connected with the receiver coil to receive the first output AC power. A second output AC power is outputted from the second coil. A turn ratio of the first coil to the second coil is larger than a turn ratio of the transmitter coil to the receiver coil.