In the previous paper or analysis of a valve seal, it was shown that sealing mechanism of some valves which have a seal of cylindrical type can be analyzed theoretically by using the cylinder theory on condition that a valve is in the pressure of normal flow and the valve shaft has no influence on performance of valves. But it is recognized distinctly from experiment that the valve shaft and its bearing have great influence on shutoff-performance of valves. In this work, taking account of the valve shaft, the method is applied to analyze sealing mechanism of a valve seal in no flow and bidirectional flow, and developed for analysis of the behavior of a valve itself. This method yields results which are consistent with behavior of a sealing device, besides it gives good explanation for the particular behavior of a valve.