To provide a projection optical system in which color aberration can be satisfactorily corrected and a highly detailed pattern can be projected with high resolution without bringing about high cost, and to provide a projection exposure apparatus in which an extremely detailed pattern image of a projection original plate can be satisfactorily projection-exposed on a substrate and a projection exposure method therefor.

The projection optical system includes a refractive optical member which consists of at least two kinds of fluoride materials, and satisfies 0.4<Mx2/Mx1<0.87, when an effective diameter of a surface having the maximum effective diameter in the refractive optical member consisting of a 1st fluoride material is set to Mx1, the effective diameter of the surface having the maximum effective diameter in the refractive optical member consisting of a 2nd fluoride material is set to Mx2, and Mx1 is larger than Mx2. Further, the projection exposure apparatus includes the projection optical system and a narrowed light source which supplies exposure light having a linewidth narrower than a natural linewidth thereof.