An energy irradiation device for medical use to irradiate a living body with energy includes a data storage for storing data indicative of correlations between information about bloodstream quantities and amounts of tissue necrosed in living bodies for a plurality of living bodies differing in bloodstream quantity that are irradiated with a predetermined quantity of the energy, a calculation unit for calculating a quantity of the energy with which to irradiate a predetermined living body based on the data stored in the data storage, the information about the bloodstream quantity in the predetermined living body, and the amount of tissue to be necrosed in the predetermined living body.
