In this study, the equipment for thermal conductivity measurement by radial heat flow method was constructed in order to measure the powder state materials like kaolin. The Kaya and Hadong kaolins were chosen as the test powders because of their abundent reserves and the thermal conductivity values of those powders were measured at the different temperatures and densities. As the results of this study, it was found that the thermal conductivity of kaolin was constant at rather low temperature range from 10 to $42^{circ}C$ and greatly affected by the density variation.