An irradiation apparatus for treating a treated body by irradiating an electron beam of high energy or the like on the foci of the treated body includes, in order to efficiently and stably performing intermittent irradiation in synchronism with respiration, a respiration synchronizing circuit for detecting a respiration state of a treated body, outputting an irradiation permission signal in synchronism with a rest period of foci which are moved by a respiration motion and outputting an irradiation prohibition signal during other periods and a beam passage change control circuit for deflecting the electron beam or the like from a correct therapy passage, causing the electron beam or the like to impinge upon a predetermined beam stopper portion during a period in which the irradiation prohibition signal is outputted from the respiration synchronizing circuit and returning the electron beam or the like to the correct therapy passage during the period in which the irradiation permission signal is outputted from the respiration synchronizing circuit.