A particle beam treatment apparatus and an irradiation nozzle apparatus achieve a beam with a small diameter by a beam scanning irradiation method, and ensure a space for installation of a beam transport chamber in the irradiation nozzle apparatus. An X-ray tube is located outside the scanning type irradiation nozzle apparatus that includes scanning magnets, while an X-ray tube is located in an irradiation nozzle apparatus in a conventional structure. An X-ray detector is located inside the irradiation nozzle apparatus. The thickness of the X-ray detector in the direction of a beam axis is smaller and the structure thereof is simpler than that of the X-ray tube. This makes it possible to ensure the space for installation of the beam transport chamber in the irradiation nozzle apparatus and to increase the length of the beam transport chamber that is included in the irradiation nozzle apparatus. It is, therefore, possible to suppress scattering of a beam due to air during transport of the beam and reduce the diameter of the beam compared with a conventional apparatus.
