[Problem] To provide a cover bonding product fabrication method with which it is possible to perform complex sewing such as zigzag stitching, double stitching, and embroidery with a pattern sewing machine via automated operation, regardless of the size of a curved surface of the cover bonding product. [Solution] According to the present invention, a method for determining a sewing pattern on a base material includes: (1) an analysis step for measuring and analyzing an expansion rate of a cover when the cover is vacuum-formed on the base material; (2) a specifying step for specifying, on the basis of the measured expansion rate, a range where the expansion rate is 130% or lower; and (3) a sewing pattern determination step for determining a sewing pattern in the range where the expansion rate is 130% or lower.