All government buildings in Korea are required to set indoor temperature above 28 °C (82.4 °F) and some commercial building using energy over 2,000 TOE should set above 26 °C (78.8 °F). However, much research has insisted that productivity of office workers is considerably influenced by the thermal environment. As the comfort zone of 0.5 Clo condition on ASHRAE Standard 55-2004, 27 °C (80.6 °F) is the boundary between comfort and discomfort. In this study, the effect of the set-point temperature on occupant's thermal comfort and energy demand in an office building equipped with VRF system will be analyzed. The indoor set-point temperature was set at 26 °C (78.8 °F) and 27 °C(80.6 °F) in summer. The result of this study could be a baseline data for finding an upper limit of the indoor temperature considering the energy use and thermal comfort in office building.