Provided is an inflatable prosthesis for aiding penile erection and augmentation for being disposed between the outer skin and the pair of corpus cavernosa of a patient's penis. The inflatable prosthesis comprises a contractible cylinder body (10) provided with a cavity (11) therein and a liquid passage (12) at the rear portion thereof; a preferably elastic or flexible head ring (20) with an annular body; a means for coupling the head ring with the front portion of the cylinder body (10); and a liquid pump (50) coupled with the liquid passage (12) of the cylinder body (10). According to the present invention, the possibility of causing damage to the penis, particularly the corpus cavernosum, may be reduced.