Abstract: A butterfly valve includes a body having pipe connecting parts forming two opposite ends thereof and a cylindrical flow path interconnecting the pipe connecting parts, a stem attached rotatably at the central part of the body diametrically across the cylindrical flow path, a lever handle connected non-rotatably to the external leading end of the stem, and a disc formed by joining two substantially circular metallic plates in a mutually opposed manner, coating the entire outer surfaces of the metallic plates with a corrosionproof, resilient material, and boring a stem-insertion hole between the two joined metallic plates in the central diametric position thereof and disposed inside the cylindrical flow path of the body for accommodating the stem non-rotatably within the stem-insertion hole thereof. An externally open groove having a substantially U-shaped cross section is formed in the joint periphery of the two joined metallic plates of the disc.