Temperature of a swash plate of an axial piston pump was measured and seven kinds of hydraulic oils were assessed. Five thermo-couples were embedded in the swash plate and one thermistor was placed in the suction conduit of the pump. The test oils were mineral and synthetic type oils with the viscosity grade of 32 to 46, adding friction modifiers. The maximum discharge pressure was 20 MPa, discharge flow rate was 161/min, and the inlet oil temperature was 30℃. At the atmospheric to maximum discharge pressures, the temperatures, flow rates and the torque were measured, and then the swash plate temperature rises and the pump performance curve were obtained. In conclusion, i) A low viscous oil with the friction modifier gave a lower temperature rise; ii) As the discharge pressure increased, the temperature rises became larger, and iii) The types of the oils tested less influenced the performance curves.