PURPOSE: To enable the execution of highly accurate measurement even at a high temperature by metallizing the outer surface of a column of a dielectric to be measured with platinum and by making the thickness thereof equal to or larger than the skin depth of a microwave which is determined by the frequency of a measuring microwave and the electric physical property value of the platinum.

CONSTITUTION: The outer surface of a column 11 of a dielectric to be measured is metallized with platinum 12 and the thickness thereof is made equal to or larger than the skin depth of a microwave which is determined by the frequency of a measuring microwave and the electric physical property value of the platinum. At the time of metallization with the platinum 12, microwave coupling holes 13 metallized with nonplatinum and having a diameter of 2-8mm are left in two places on the lateral side of the column 11 corresponding to each other. Accordingly, the column is a solid resonator by a cavity resonator method. Resonance is generated by injecting the microwave into the resonator from one of the holes 13 through an antenna for the microwave and the state of the resonance is detected from the other hole 13 by a similar antenna. On the occasion, resistance to a high temperature of about 1500 degrees is given by the use of the platinum 12, and since the resonator has no flange contact surface, highly accurate measurement of a dimensionless quantity Q showing the acuteness of the resonance is enabled.