Thermal creep flow of a rarefied gas in a circular tube, the flow resulting from a thermal gradient, was analyzed on the basis of the kinetic theory of gases. The thermo-molecular pressure ratio due to the thermal transpiration effect was measured by use of the relative method, and the conductance of the creep flow was obtained from thermo-molecular pressure ratio data. As a result, a semi-empirical formula expressing the volume flow rate of the thermal creep flow and one expressing the thermal transpiration effect were derived. They are in fairly good agreement with the experimental data over the whole range of inverse Knudsen number.