In this paper, suction performances of bent axis type and swash plate type axial piston pumps are investigated experimentally. At the same time, the relationship between the pressure in the cylinder and the bubble formation is observed using a simulated model of piston pump whose cylinder is made of transparent plastic. The experimental results about critical suction performances of axial piston pumps are compared with the evaluated results obtained in the 1st report. And it becomes clear that the agreement of both results is fairly good.