In this study, a cavitation occurrence in a piston-pump inlet was investigated by simulating the pressuredistribution, according to the inlet shape of a variable-displacement swash-plate piston pump that supplieshigh-pressure oil to control the hydraulic system of a marine engine. Two types of pump inlets with differentshapes were cast into impression models, and the models were reverse-engineered by 3D scanning. Then, thehydraulic-pressure distribution was analyzed through finite-element analysis. The results of the analysisconfirmed that cavitation occurs more easily in the inlet with a steeper slope during pump operation becausethe inlet pressure on the valve plate is lower than that of the other pump with a gentler inlet slope.