PROBLEM TO BE SOLVED: To provide a cancer thermotherapy device capable of effectively performing the thermotherapy against cancer in a human body by heating the depth of the human body effectively.
SOLUTION: The device is provided with a rectangular-parallelepiped hollow resonator 1 and a loop antenna 2 on its upper/inner wall surface 1A. The antenna 2 is fixed so that its loop surface may be orthogonal and adjacent to the surface 1A and may be parallel to the side inner wall surfaces 1B and 1C of the resonator 1 opposing each other. Then, high-frequency oscillation introduced into the resonator 1 resonates to an exciting mode of fixed intensity in the direction parallel to the surfaces 1B and 1C. The human body 6 is put in the resonator 1 parallel with the surface 1B and 1C, and the cancer part is exposed to the high-frequency emission.