Surface weighting factors of the whole human body for both standing and seated postures are calculated based on the numerical calculation of angle factors for the simple prediction of the thermal radiation field. To verify the validity of these factors, they are compared with previous results by Nakamura or Olesen. As a result, surface weighting factors are different from previous results which are always constant independent of the scale of indoor spaces. Especially, surface weighting factor to the under surface for a standing posture is approximately 4 times larger than that of Nakamura in the small indoor spaces. The position of human body and the scale of indoor spaces have influence on surface weighting factors. In addition, appropriate surface weighting factors are proposed corresponding to the scale of indoor spaces, which enables to the accurate prediction of the thermal radiation field.