An ultrasound medical treatment system capable of determining the hot spot at high spatial resolution, and preventing the displacement of the hot spot from the focal point. In the system, the imaging device for obtaining image data of a treatment portion containing a treatment target and an irradiation device for applying radiation onto the treatment target are controlled in such a manner that the imaging device is controlled to obtain hot spot detection image data after the irradiation device is controlled to apply radiation at a prescribed level, so that a hot spot indicating a change due to a temperature change caused by the radiation at the prescribed level can be detected from the hot spot detection image data. The irradiation device is then controlled to apply a treatment radiation at a treatment level higher than the prescribed level according to the detected hot spot.