Recently, Photodynamic Therapy (PDT) using light has been expected as a low invasive treatment because it has fewer side effects than conventional cancer treatments. However, current PDT is limited to the types of cancer that can be reached by cables, so it is difficult to apply PDT to cancers deep inside the body, such as pancreatic cancer. In this paper, we designed a wireless power transfer system that combines a small and lightweight receiving coil and LEDs for implantation in the body. After that, we experimented to see whether cancer cell death was induced by light irradiation in vitro using power transfer in free air space. As a result, we succeeded in inducing about 75 % of cancer cell death by 60 minutes of light irradiation at a 30 mm transfer distance. At that time, we derived an approximation of the amount of light energy required to induce cancer cell death by changing the light irradiation time, and we were able to predict the treatment time.