PURPOSE: To improve inserting ability of a device into a coelom, to improve directional property in the emission direction of microwaves, and to reliably prevent heating of a normal tissue by a method wherein the central conductor of a microwave emitting part is arranged eccentrically to the center of an external conductor.

CONSTITUTION: An insulating substance 12 and a central conductor 13 connected to a central conductor 9 of a coaxial cable 5 are disposed in an external conductor 11 of an antenna part 6. The control conductor 13 is arranged in a position situated eccentrically to a center O of the external conductor 11 of the antenna part 6. Thus, emission distribution of microwaves emitted from the antenna part 6 is such that distribution in a direction in which a distance between the central conductor 13 and the external conductor 11 is decreased is more densely effected compared with that in other direction, resulting in the possibility to provide directional property in a direction in which microwaves are emitted. This constitution improves inserting ability of a title device in a coelom 15, and performs hot heat medical treatment by microwaves simultaneously with diagnosis in a way that a microwave probe 1 is inserted in the forceps insertion channel of, for example, an endoscope.