PROBLEM TO BE SOLVED: To provide a technique capable of improving accuracy in various radiation treatment plans.SOLUTION: An information processing device includes: a simulation information acquisition unit for acquiring an average absorbed dose in an evaluation area included in an object to be obtained by simulating an action in the object of a radiation on which an irradiation condition is designated; a distribution acquisition unit for acquiring the probability density distribution of an absorbed dose with respect to an average absorbed dose in each cell or cell nucleus assumed to be included in the evaluation area; and an equivalent dose acquisition unit for acquiring an equivalent dose in an evaluation area, based on the probability density distribution of an absorbed dose with respect to an average absorbed dose in each of the cells or the cell nuclei and the average absorbed dose.
