A reconditioning apparatus is installed in each of indoor-side and outdoor-side compartments. Capacity of the reconditioning apparatus is controlled so as to cancel cooling or heating capacity of the equipment under test, and as a result, air temperature and humidity of indoor-side and outdoor-side compartments are stabilized under the JIS conditions. In addition, air temperature and humidity of controlled- temperature air space on both indoor-side and outdoor-side are controlled to reach the same temperature and humidity as in indoor- side and outdoor-side compartments, respectively. Amount of heat passing through two compartments is a known value. By determining cooling or heating capacity of the reconditioning apparatus at the stable condition, cooling or heating capacity of the equipment under test can be measured with high accuracy.