A corrector to be used in combination with an electromagnetic lens for charged particle beam to correct spherical aberration generated by the electromagnetic lens, the corrector comprising: an incident plate arranged on an incident side of the charged particle beam; an emission plate arranged on an emission side of the charged particle beam; and means for applying a voltage between the plates, wherein one of a circular aperture and a ring-shaped aperture is provided on the incident plate, another of the circular aperture and the ring-shaped aperture is provided on the emission plate, centers of the circular aperture and the ring-shaped aperture are on a center line of the charged particle beam, the incident plate and the emission plate intersect perpendicularly to the center line, φ3≥φ2>φ1 is satisfied, where a diameter of the circular aperture is φ3, an outer diameter of the ring-shaped aperture is φ2, and an inner diameter of the ring-shaped aperture is φ1, when the charged particles are of negative charge, the means for applying a voltage between the plates are configured to apply the voltage such that a potential of a plate on which the ring-shaped aperture is provided is higher than a potential of a plate on which the circular aperture is provided, and when the charged particles are of positive charge, the means for applying a voltage between the plates are configured to apply the voltage such that the potential of the plate on which the ring-shaped aperture is provided is lower than the potential of the plate on which the circular aperture is provided, and an inner portion and an outer portion of the ring-shaped aperture are configured to be at a same potential. an incident plate arranged on an incident side of the charged particle beam; an emission plate arranged on an emission side of the charged particle beam; and means for applying a voltage between the plates, wherein one of a circular aperture and a ring-shaped aperture is provided on the incident plate, another of the circular aperture and the ring-shaped aperture is provided on the emission plate, centers of the circular aperture and the ring-shaped aperture are on a center line of the charged particle beam, the incident plate and the emission plate intersect perpendicularly to the center line, φ3≥φ2>φ1 is satisfied, where a diameter of the circular aperture is φ3, an outer diameter of the ring-shaped aperture is φ2, and an inner diameter of the ring-shaped aperture is φ1, when the charged particles are of negative charge, the means for applying a voltage between the plates are configured to apply the voltage such that a potential of a plate on which the ring-shaped aperture is provided is higher than a potential of a plate on which the circular aperture is provided, and when the charged particles are of positive charge, the means for applying a voltage between the plates are configured to apply the voltage such that the potential of the plate on which the ring-shaped aperture is provided is lower than the potential of the plate on which the circular aperture is provided, and centers of the circular aperture and the ring-shaped aperture are on a center line of the charged particle beam, the incident plate and the emission plate intersect perpendicularly to the center line, φ3≥φ2>φ1 is satisfied, where a diameter of the circular aperture is φ3, an outer diameter of the ring-shaped aperture is φ2, and an inner diameter of the ring-shaped aperture is φ1, when the charged particles are of negative charge, the means for applying a voltage between the plates are configured to apply the voltage such that a potential of a plate on which the ring-shaped aperture is provided is higher than a potential of a plate on which the circular aperture is provided, and when the charged particles are of positive charge, the means for applying a voltage between the plates are configured to apply the voltage such that the potential of the plate on which the ring-shaped aperture is provided is lower than the potential of the plate on which the circular aperture is provided, and an inner portion and an outer portion of the ring-shaped aperture are configured to be at a same potential.