The tribological properties of the mechanical seal lubricated with the refrigerating machine oil with oiliness and anti-wear additives were studied by using a thrust-washer test rig. Friction tests were carried out under bath lubrication for the base oil, oil A (base oil+Oleic acid and Tricresyl phosphate at 5mmol/kg) and oil B (base oil+Oleic acid and Tricresyl phosphate at 10mmol/kg, 5mmol/kg, respectively). From the tests, the following results were obtained. (1) The coefficient of friction μ decreased in following order at sliding velocity 3.93m/s: base oil>oilA>oil B. The value of μ with oil B was 0.08〜0.10, and was about 1/2 times as small as that with base oil. (2) The amount of friction loss decreased in following order: base oil>oil A>oil B. Therefore, the additives of Oleic acid and Tricresyl phosphate showed significant improvements in tribological properties of the refrigerating machine oil.