A spot determination unit classifies an irradiation region to be irradiated with a charged particle beam into a plurality of layers in an irradiation direction of the charged particle beam, and arranges a plurality of irradiation spots in the plurality of layers. The irradiation spots are classified into groups in accordance with at least either a distance between one irradiation spot and another irradiation spot which are arranged in the same layer or a target irradiation dose of each irradiation spot. A plan is prepared for continuously emitting the charged particle beam while the irradiation position is changed from an irradiation spot belonging to a certain group to a subsequent irradiation spot, and so as to stop emitting the charged particle beam while the irradiation position is changed from an irradiation spot belonging to a certain group to an irradiation spot belonging to another group located in the same layer.
