The radiation therapy system of the present invention includes: a proton beam generating device 103； a rotary irradiation device 105 that irradiates a proton beam generated by the proton beam generating device 103 toward a target 201 in an irradiated body 111； a control device 102a that applies a proton beam The generator 103 and the rotary irradiation device 105 perform control； a converter 303 is provided on the object 111 to be irradiated； and a signal processing device 302 determines whether or not a sound wave is generated from the reference mark 101 based on a signal waveform measured by the converter 303. This determines whether the proton beam is irradiated at the planned location.本發明之放射線治療系統具備：質子束產生裝置103；旋轉式照射裝置105，其將由質子束產生裝置103產生之質子束朝向被照射體111中之靶201照射；控制裝置102a，其對質子束產生裝置103及旋轉式照射裝置105進行控制；轉換器303，其設置於被照射體111；及信號處理裝置302，其基於由轉換器303測定之信號波形，判定有無自基準標記101產生音波，藉此判定質子束是否照射於計劃之位置。
