In this study, the result of the basic investigation of office buildings in the fiscal year 2008 by DECC (Data-base for Energy Consumption of Commercial Buildings) was shown. Questionnaire survey of office buildings has been carried out national wide, which helped to understand the actual usage pattern of energy consumption. There were 1128 valid responses in this investigation and the national averages of the annual primary energy consumption per square meter was 1738[MJ/m 2-Year].In order to identify the influential factor, the multiple regression analysis was done and from the result, you can see that the largest impact factor on total energy consumption was floor area and the coefficient of determination was over 0.8. The impact factors on energy consumption per square meter were cooling period, density of users and floor area. On the other hand, the coefficient of determination was about 0.25.