A prediction of the thermal response of a steel beam installed beneath a ceiling and exposed to a localized fire source was performed by using CFD model. The validity of this calculation has been verified by results of experiments. Concerning the heat flux, the difference between analytical results and experimental values increases with increasing dimensionless heat release rate QHB*≡Q/ρCPT0 g1/2HB5/2. In the case of the lower flange, the difference between the analytical result and experimental value increases rapidly over the range of QHB* from 0.3 to 0.5, reaching the maximum value of about 27(kW/m²). From the results of the investigation, it has become clear that the prediction is possible with a practical accuracy about the convection part of heat transfer. However, it is necessary to model minutely about combustion and radiation.