According to one embodiment, contactless power transfer transformer includes power transmission coil and power reception coil. At least one of the power transmission coil and the power reception coil is configured by coupled and both-sides wound coil. The coupled and both-sides wound coil is configured by both-sides wound coils. One of magnetic poles of one of the both-sides wound coils is connected to one of the magnetic poles of adjacent one of the both-sides wound coils. Directions of magnetic fluxes toward corresponding coil from each of the magnetic poles connected to each other are identical. The both-sides wound coils are selected so that leakage magnetic flux around moving body does not exceed predetermined value. Number of the both-sides wound coils is set so that value obtained by multiplying power transfer capacity of one of the both-sides wound coils by the number satisfies capacity of the transformer.