Effects of viscosity and oiliness of lubricant film on its wear property are studied by stick-slip analyzing apparatus. The wear properties of various lubricant films are compared with each other by measuring the increase of friction coefficient during repetition of sliding. As the crlterions for the comparison of wear properties of lubricant films are used both the increase of friction coefficient during repeition of runs on the same track and the critical number of runs when the continuous sliding changes to stick-slip. As the result of experiment it is found that not only the oiliness of lubricant but also its viscosity affects so much on the wear of the film ; low viscosity lubricant film flows more easily than high viscosity film into and wets the before frictional track, preventing the catastrophic rise of friction coefficient.