Radiation therapy simulation device capable of enhancing simulation precision for therapy dose during radiation therapy

The present invention provides a radiation therapy simulation device capable of enhancing the simulation precision of therapy dose during the radiation therapy. The radiation therapy simulation device according to this invention (10) comprises: a computation unit (5) for calculating the therapy dose distribution of radiation irradiated on the patient during the radiation therapy; and, an information memory unit (3) for storing the medicine dosage information regarding sensitizer or protective agent applied to the patient during the radiation therapy; wherein, the computation unit (5) calculates the therapy dose distribution according the medicine dosage information stored in the information memory portion (3).