A contactless power transfer transformer comprising: a both-sides wound coil that includes an inter-magnetic-pole core portion between two magnetic pole portions, a winding wire of the coil being wound around a wound region and both sides of the inter-magnetic-pole core portion, wherein the inter-magnetic-pole core portion includes: a plurality of separate magnetic members that connect to each of the two magnetic pole portions, and are arranged with a spacing therebetween and in parallel with each other; and heat conductors that are alternately arranged with respect to the separate magnetic members on a plane formed by the separate magnetic members so as to be in contact with the separate magnetic members, heat generated by the separate magnetic members is guided to the outside of the wound region of the inter-magnetic-pole core portion through the heat conductors, and is dissipated, heat conductors connecting portions of the transformer that adhere to the heat conductors are arranged at both end portions of the inter-magnetic-pole core portion arranged away from the wound region, the heat guided through the heat conductors is dissipated through the heat conductors connecting portions, and the heat conductors are divided into half at a middle position between the heat conductors connecting portions arranged at the both end portions away from the wound region. a both-sides wound coil that includes an inter-magnetic-pole core portion between two magnetic pole portions, a winding wire of the coil being wound around a wound region and both sides of the inter-magnetic-pole core portion, wherein the inter-magnetic-pole core portion includes: a plurality of separate magnetic members that connect to each of the two magnetic pole portions, and are arranged with a spacing therebetween and in parallel with each other; and heat conductors that are alternately arranged with respect to the separate magnetic members on a plane formed by the separate magnetic members so as to be in contact with the separate magnetic members, heat generated by the separate magnetic members is guided to the outside of the wound region of the inter-magnetic-pole core portion through the heat conductors, and is dissipated, heat conductors connecting portions of the transformer that adhere to the heat conductors are arranged at both end portions of the inter-magnetic-pole core portion arranged away from the wound region, the heat guided through the heat conductors is dissipated through the heat conductors connecting portions, and the heat conductors are divided into half at a middle position between the heat conductors connecting portions arranged at the both end portions away from the wound region. a plurality of separate magnetic members that connect to each of the two magnetic pole portions, and are arranged with a spacing therebetween and in parallel with each other; and heat conductors that are alternately arranged with respect to the separate magnetic members on a plane formed by the separate magnetic members so as to be in contact with the separate magnetic members, heat generated by the separate magnetic members is guided to the outside of the wound region of the inter-magnetic-pole core portion through the heat conductors, and is dissipated, heat conductors connecting portions of the transformer that adhere to the heat conductors are arranged at both end portions of the inter-magnetic-pole core portion arranged away from the wound region, the heat guided through the heat conductors is dissipated through the heat conductors connecting portions, and the heat conductors are divided into half at a middle position between the heat conductors connecting portions arranged at the both end portions away from the wound region.