The present invention relates to an erection assistance device that includes: an elastic penis implant which has a semi-cylindrical shape, with its lower pan opened, and is processed to be inserted between an epidermis and a cavernous body of a penis a storing part which is connected to the expansive part via connection pipes and stores a fluid to be supplied into the expansive part and a pump which is provided in the middle of the connection pipes, wherein the pump is manipulated to adjust a degree of expansion of the penis implant.
