Abstract: According to an embodiment, a particle beam treatment system has: a CT device that is a three-dimensional image acquisition part installed in a treatment room for acquisition of a three-dimensional internal image on a day of treatment; a dose distribution display part that displays a dose distribution in the three-dimensional image acquired on the day of treatment and a dose distribution in treatment plan data designed in advance; a treatment management device that is a selection part to select whether or not to change the treatment plan data based on the dose distribution in the three-dimensional image acquired on the day of treatment and the dose distribution in treatment plan data designed in advance; and an irradiation part that irradiates an affected part with a particle beam according to the treatment plan data based on selection made by the treatment management device.