Energy Saving has become the most important issue from all over the world. Also, government encourages the use of system air-conditioner which is able to secure the thermal comfort of occupant and effectively control the thermal environment in office building. Moreover, due to the convenience of the usage and high C.O.P., the demand for system air-conditioner are highly increased in the world. In this study, indoor thermal environment and thermal comfort of occupant where the temperature is controlled by system air-conditioner were analyzed by field measurement. In this paper, the field measurement outline and the measurement results will be described.