A projection optical system having a multilayered film mirror arranged to provide an approximately uniform reflectance throughout a predetermined light incidence angle range to thereby assure a desired optical performance. A projection exposure apparatus having such a projection optical system, and a device manufacturing method using such an exposure apparatus. A non-periodic film is used in a reflection multilayered film upon a mirror having a largest light incidence angle range or a mirror having a largest average of light incidence angle, and this effectively reduces a pupil transmittance distribution in the projection optical system.