1. A device for outputting a charged particle beam to irradiate the charged particle beam on a target, the device comprising: a charged particle beam generator which generates the charged particle beam; an irradiation device which includes a range modulation device having a thickness varying in a direction of propagation of the charged particle beam outputted from the charged particle beam generator to change the energy of the passing charged particle beam so that a spread-out Bragg peak is formed in the target to be irradiated, and which outputs the charged particle beam which passed the range modulation device to the target to be irradiated; a dose measurement device which measures the dose of the charged particle beam at a position downstream of the range modulation device in the direction of charged particle beam propagation; and a spread-out Bragg peak calculation device which calculates a spread-out Bragg peak based on the dose value measured by the dose measurement device.