To raise workability in sewing an upholstery material with a sewing machine, concerning an upholstery material sewing method for joining a plurality of upholstery pieces to form the upholstery material, sewing the material in a bag shape, injecting a foaming liquid for molding a pad to an inner part, and integrally molding the pad with the upholstery material.

Two sewing needles A, B are arranged side by side in a direction for feeding the upholstery materials 3, 4 by the sewing machine. The upholstery material 3, 4 are joined by allowing the feeding pitch L of the sewing machine to be concentric with the pitch L of the two sewing needles A, B.