Induction heating type hyperthermia treatment needs both high magnetic fields (> 2 mT) and a few hundred kHz inside of a body to heat magnetic particles and implant materials up to 43°C. We proposed the double-pancake type coils sandwiching human body。 The exciting coils of human scale could generate magnetic fields with both magnitude and frequency required to a medical treatment. In order to make magnetic fields inside a deep body further increase, we proposed that a back yoke as magnetic materials was added to both coils. The paper discussed magnetic- and electrical-circuit characteristics of the coils with a magnetic sheet and ferrite as back yoke.