PURPOSE: To improve the measuring efficiency by shortening the heating time and to prevent the lowering of the heating efficiency by heating a dielectric resonator to be measured with microwave in a vessel, and simultaneously contriving the matching of the dielectric resonator with an input loop.

CONSTITUTION: A resonant frequency in the room temperature is measured, then the microwave from a microwave device is coupled with a resonant frequency mode in the vessel 1 through the input loop 6, and by this microwave heating the dielectric sample 2 to be measured is heated. In this state the resonant frequency is again measured, and by comparing it with the resonant frequency at the room temperature, the temperature characteristic is obtained. By rotating a driving motor 10 of a matching control means 11 a semi-rigid cable 5, since an input cable 6 is set at the stage of revolutionable so that the projection area of the central axis A direction is changed. Consequently, the matching of the impedance of the resonator with the outside Q of the input side is contrived, the energy loss is controlled, the heating efficiency is highly maintained.