Observation using an FIB image is enabled without causing any damage to a designated region. To this end, an ion beam scanning-prohibited region is set in a sample by using an image acquired by a charged particle beam other than an ion beam, or an image prepared as external data as a peripheral image including the designated region of a sample. Thereafter, the image used to set the ion beam scanning-prohibited region is exactly superimposed on an FIB image acquired for regions except the ion beam scanning-prohibited region, thereby forming an image including the ion beam scanning-prohibited region on which ion beam scanning has not been performed.