Mechanical properties of plastics greatly depend on temperature, which follows that the temperature rise in meshing gear teeth must be crucial to the load capacity of a gear pair. The present study will provide a method for estimating it. For this purpose, twin-disc tests with plastic test roller and steel roller allowed temperature-rise in test rollers to be measured. The twin-disc tests under the various applied loads and surface sliding velocities defined the change in the surface temperature of test rollers. The measured surface temperature gradually increased during the twin-disc test and converged to a certain level after some minutes. The difference between the initial temperature and the converged one is temperature-rise. The temperature rise depended on contact stress and sliding velocity. As a result, the temperature rise in test rollers has an approximately linear relationship with the PV value, which is the product of the maximum contact pressure (P) and the sliding velocity (V) between roller surfaces. This result could be fundamental data for estimating the temperature rise in meshing gear teeth.