In this paper, we proposed a new contactless power-signal transmission device using electromagnetic coupling for a Functional Electrical Stimulation (FES) system, which consists of two coils. With the primary coil outside and the secondary inside the body, the in vivo coil composed of a coupling of two parts, one to receive power and one to receive signal, each at a different radio frequency. In this study, our approach is based on a structure to implement a simultaneous power-signal transmission system, which enables power and signal for muscle stimulation to be concurrently transferred from outside the body, while allowing for the separation inside. Moreover, the induced voltage of the magnetic flux on signal transmission, suppressed to 0.15 V, the output signal voltage of 2 V or more was established at a signal frequency of 7.7 MHz, thus leading to stable operation. The study also aimed to reach for higher power output of the secondary coil. Index Terms - Functional electrical stimulation (FES), Implanted device, contactless power-signal transmission.