The motor function lost by traffic accidents etc. can be rebuilt or assisted by applying appropriate electric stimulation from the outside. This treatment method is called “Functional Electrical Stimulation (FES).” We plan to create a completely implantable FES system for the next generation of FESs. This is a contactless power and signal transmission method using electromagnetic coupling between a primary coil located outside the body and a secondary coil implanted inside. In this research, we designed an implantable stimulator which could receive both power and signal at the same time. This stimulator has a microminiature shape of about 10 mm in length and consists of two types of coils, one for power receiving and the other for signal receiving. The signal receiving coil has a structure which can reduce the influence of the magnetic field on the power supply without using a filter. This time, we examined the shape of a stimulator that can receive higher power and higher signal voltage experimentally.