The thermal conductivities of superconductors (Nb3Sn, V3Ga) dependent on the temperature are presented. We studied by using the steady-state comparative plate method. This comparative method is suitable for superconductors at low-temperatures. In this method, a reference sample of lead was placed in series with the unknown superconductor specimen. This comparative method has the advantages of simpler specimen fabrications and simpler equipment. Temperature measurements were made with AuFe-Cr thermocouples embedded in grooves on the superconductor specimens. The experimental data on thermal conductivities of superconductors have clearly changed to lower values, bounding on the transition conductivities of superconductors have clearly changed to lower values, bounding on the transition temperatures of superconductors. These non-dimensional thermal conductivites which are normalized by the values at the transition temperature of Nb3Sn and V3Ga show similar thermal conductivity trends depending on the non-dimensional temperature.