A microwave providing device is provided, which is capable of effectively extending the coagulation range of a treatment target tissue by setting the conditions for intermittently providing microwaves. An output controller controls a microwave generator based on a first efficiency of dielectric heating by microwaves with respect to a cumulative radiation period of microwaves radiated intermittently to a treatment target tissue S and a second efficiency of dielectric heating by microwaves with respect to a cumulative radiation period of microwaves radiated continuously to the treatment target tissue so that microwaves are intermittently radiated at least after a reference cumulative radiation period that is set in advance as a cumulative radiation period at which the first efficiency becomes larger than the second efficiency.
