This treatment planning device calculates position information for specific locations for a plurality of times corresponding to a time course on the basis of the positions of markers positioned in the vicinity of the specific locations, and generates a three-dimensional range for the specific locations for each of the plurality of times. In addition, the treatment planning device generates representative range information, which represents a range that includes the entire three-dimensional ranges for the specific locations for each of the plurality of times, tracks the position information for the specific locations for each of the plurality of times, and calculates the amount of radiation to be emitted in the range for the specific locations represented by representative range information when radiation is emitted for a prescribed time period in the range for the specific locations represented by the representative range information.
