An exposure apparatus includes an illumination optical system that includes an optical integrator for forming a secondary light source from the light, and a variable stop arranged at or near a position where the secondary light source is formed, the diameter variable stop that defines a NA of the illumination optical system, a projection optical system that includes an aperture stop arranged at a position substantially optically conjugate with the variable stop, the aperture stop defining a numerical aperture of the projection optical system, and a controller for controlling the aperture diameter of the variable stop as the aperture diameter varies so that an image of the secondary light source can fall within the aperture diameter of the aperture stop.