An illumination optical apparatus for illuminating a pattern on a mask with illumination light through a pupil plane of the illumination optical apparatus, the illumination light being distributed in a region on the pupil plane away from an optical axis of the illumination apparatus, the illumination optical apparatus comprising: a light limiting member (9a, 9b) for changing an incidence angle range of the illumination light to the mask and arranged in an optical path of the illumination light, the apparatus being characterized by: a birefringent member arranged in the optical path on an exit side of the light limiting member; and an optical integrator arranged in the optical path on an exit side of the birefringent member, wherein a first thickness of the birefringent member in an optical path of a first ray of the illumination light is different from a second thickness of the birefringent member in an optical path of a second ray of the illumination light, the first ray being a ray which passes through a first region in the region on the pupil plane, the second ray being a ray which passes through a second region in the region different from the first region on the pupil plane, and wherein the birefringent member is configured to change a polarization state of the illumination light, which arrives from the light limiting member in a linear polarization state having a predetermined single polarization direction, so that a polarization direction of the illumination light on the pupil plane in the first and second regions is substantially coincident with a circumferential direction about the optical axis. a light limiting member (9a, 9b) for changing an incidence angle range of the illumination light to the mask and arranged in an optical path of the illumination light, the apparatus being characterized by: a birefringent member arranged in the optical path on an exit side of the light limiting member; and an optical integrator arranged in the optical path on an exit side of the birefringent member, wherein a first thickness of the birefringent member in an optical path of a first ray of the illumination light is different from a second thickness of the birefringent member in an optical path of a second ray of the illumination light, the first ray being a ray which passes through a first region in the region on the pupil plane, the second ray being a ray which passes through a second region in the region different from the first region on the pupil plane, and wherein the birefringent member is configured to change a polarization state of the illumination light, which arrives from the light limiting member in a linear polarization state having a predetermined single polarization direction, so that a polarization direction of the illumination light on the pupil plane in the first and second regions is substantially coincident with a circumferential direction about the optical axis. a birefringent member arranged in the optical path on an exit side of the light limiting member; and an optical integrator arranged in the optical path on an exit side of the birefringent member, wherein a first thickness of the birefringent member in an optical path of a first ray of the illumination light is different from a second thickness of the birefringent member in an optical path of a second ray of the illumination light, the first ray being a ray which passes through a first region in the region on the pupil plane, the second ray being a ray which passes through a second region in the region different from the first region on the pupil plane, and wherein the birefringent member is configured to change a polarization state of the illumination light, which arrives from the light limiting member in a linear polarization state having a predetermined single polarization direction, so that a polarization direction of the illumination light on the pupil plane in the first and second regions is substantially coincident with a circumferential direction about the optical axis.