A shield device for a resonance type contactless power transmission system that reduces adverse influence on power transmission efficiency without unnecessarily increasing space for installing the shield device is provided. A shield device of the resonance type contactless power transmission system includes cylindrical shield members, which are provided in a power supply unit and a power receiving unit, respectively. The distance between the bottom of the shield member provided in the power supply unit and the primary-side resonance coil and the distance between the bottom of the shield member provided in the power receiving unit and the secondary-side resonance coil are both set to be greater than a distance between the primary-side resonance coil and the secondary-side resonance coil that allows power transmission at the maximum efficiency from the power supply unit to the power receiving unit.