To reduce processing time for shape correction processing and smoothing processing in processing of an optical element requiring high shape accuracy.

A workpiece surface 100 is processed by simultaneously irradiating a plurality of charged-particle beams to the workpiece surface 100 in the same relative movement. A first charged-particle beam of the plurality of the charged-particle beams performing the same relative movement is an ion beam 101 for shape correction processing which performs the shape correction processing by variably controlling scanning speed along a raster scanning locus 103. A second charged-particle beam is an ion beam 102 for smoothing processing which performs the smoothing processing by variably controlling a pulse width and a current amount corresponding to the change of the scanning speed. A plurality of processings in which the distribution of the number of unit attainment particles is different at the workpiece surface 100 are simultaneously carried out so that processing time is reduced.