A method of manufacturing a radio frequency accelerator that accelerates charged particles injected into a second-stage linear accelerator (3) from a first-stage linear accelerator (2) includes a step of setting a value of a power distribution factor R for the power distributor (7) to supply radio frequency power to the second-stage linear accelerator (3) and a value of a ratio L/ω of a length L of the matching section (8) between the outlet of the first-stage linear accelerator (2) and the inlet of the second-stage linear accelerator (3) to the angular frequency ω of the radio frequency power, so that a charged particle beam is extracted from the second-stage linear accelerator (3) over a range of the total radio frequency power wider than a widest allowable range among allowable total radio frequency power ranges determined for each phase of charged particles on the basis of phase acceptance of the second-stage accelerator (3).
