A catadioptric imaging optical system of a high numerical aperture in which various aberrations are properly corrected without using a reflection surface having an aspherical shape of high order or a reciprocal optical element. The catadioptric imaging optical system forms an image of a first plane on a second plane and includes a first imaging system for forming a first intermediate image of the first plane based on light from the first plane, a second imaging system having two concave reflection mirrors for forming a second intermediate image of the first plane based on light from the first intermediate image, and a third imaging system for forming a final image of the first plane on the second plane based on light from the second intermediate image. The two concave reflection mirrors have prolate spheroidal-shaped reflection surfaces.