A scanning exposure apparatus for transferring a pattern of an original onto a substrate, includes a flexible blade, arranged between a light source and the original, for defining a width of an illumination area on the original in a scan direction, a first drive system to move the blade in the scan direction at a first position in the illumination area in an orthogonal direction that is orthogonal to the scan direction, and a second drive system to move the blade in the scan direction at a second position outside the illumination area in the orthogonal direction, wherein the first and second positions are arranged so that a position of the blade in the scan direction is maintained still within a predetermined tolerance, at an end position of the illumination area in the orthogonal direction.