To provide an aberration correcting structure enabling both a long-focus aberration correcting function and a short-focus aberration correcting function.

By using a conventional aberration corrector structure disposing two rotation-symmetry lenses between two multi-pole lenses, this aberration corrector disposes three rotation symmetry lenses between an objective lens and the multi-pole lens instead of the conventional arrangement in which two rotationally symmetric lenses are disposed therebetween. When the focal length of the objective lens is long, a set of two of the three rotation symmetry lenses disposed between the objective lens and the multi-pole lens is used for correction of aberration. Further, when the focal length of the objective lens is short for high resolution observation, etc, another set of two of the three rotation symmetry lenses disposed between the objective lens and the multi-pole lens which is different from the set of two rotation symmetry lenses used for longer focal length is used for correction of aberration.