An inflatable ball includes interconnected first and second half ball bodies. The first half ball body has a first half ball wall with first inner and outer wall surfaces, and a first rib structure formed as one piece with the first half ball wall and projecting from one of the first inner and outer wall surfaces. The first half ball wall has a through hole extending through the first inner and outer wall surfaces, and a first annular connecting edge interconnecting circumferential ends of the first inner and outer wall surfaces. The second half ball body has a second half ball wall with second inner and outer wall surfaces, and a second rib structure projecting from one of the second inner and outer wall surfaces. A valve unit is attached to the first half ball body in connection with the through hole.