Provided are a substrate processing apparatus, whereby high-quality substrates can be manufactured with high productivity, a device manufacturing method, and a mask. The present invention is provided with: a mask supporting member that supports a mask pattern such that the pattern is supported along a first surface that is curved in a cylindrical surface shape at a predetermined curvature in a lighting region; a substrate supporting member that supports the substrate such that the substrate is supported along a predetermined second surface in a projection region; and a drive mechanism, which rotates the mask supporting member such that the mask pattern moves in the predetermined scanning exposure direction, and which also moves the substrate supporting member such that the substrate moves in the scanning exposure direction. The mask supporting member satisfies formula of 1.3≤L/&phgr;≤3.8, where a diameter of the first surface is represented by &phgr;, and a first surface length in the direction orthogonal to the scanning exposure direction is represented by L.