A treatment planning apparatus 501 or a clinical decision support apparatus 701 calculates a dose distribution, calculates the damage to a normal tissue for a plurality of number of times of radiation irradiation based on the calculated dose distribution, and displays at least one or more calculated damages to the normal tissues on display apparatuses 603 and 703 or outputs the same to an outside of the apparatuses 501 and 701. Accordingly, since effects can be calculated for a plurality of number of times of irradiation, the optimum number of time of irradiation can be presented, and an operator and a doctor can be presented with a suitable decision material of a radiation irradiation planning.
