Thermal behavior of friction property on ultra-thin perfuruoropolyether (PFPE) lubricant film on diamond like carbon (DLC) overcoat of magnetic disks was studied using newly developed pin-on-disk tester with laser irradiation heating. Friction coefficient of lubricated DLC surface with Z-tetraol decreased with heated temperature. On the other hand, that of lubricated disks with Z-03 gradually decreased around 120°C and increased over 120°C. This minimal point might mean the transition temperature. Friction coefficient of both lubricant films on DLC surface depended on the kinematic viscosity of lubricant materials and the lubricant film with lower kinematic viscosity showed lower friction coefficient.