An apparatus for optical power transmission capable of reducing a number of photo cells and improving a power transmission efficiency, and an optically powered system using the apparatus capable of maximizing lifetime of light sources. The apparatus includes an alternating current transformer for transforming the electric power to a desired level for a load. The system further includes a device for detecting magnitude of the electric power, and a device for controlling an amount of light emission by the light source in accordance with the detected magnitude of the electric power such that the magnitude of the electric power to be given to the load is maintained to be substantially constant.