A scanning exposure apparatus for performing exposure of a substrate to light via an original while the substrate and the original are scanned. The apparatus includes a projection optical system to project light from the original onto the substrate, a stage to hold the substrate and to move in a scanning direction perpendicular to an optical axis of the projection optical system, and a focus detector to detect a position of a surface region of the substrate in a direction of the optical axis. The apparatus is configured (i) to detect the position of the surface region with respect to each of a plurality of measurement points and with respect to each of a plurality of shot regions of the substrate, (ii) to average the detected positions over the plurality of shot regions with respect to each of the plurality of measurement points, (iii) to obtain a function which approximates the averaged positions respectively obtained, (iv) to calculate a difference between each of the averaged positions and a value of the obtained function with respect to each of the plurality of measurement points, (v) to offset a position detected by the focus detector with respect to each of the plurality of measurement points with a corresponding one of the calculated differences, and (vi) to control a position of the stage based on each of the offset positions during the exposure.