In a braiding yarn made of expanded graphite 1, a reinforcing wire member 3 made of a stainless steel wire which is easily plastically deformed, and having a diameter of 0.05 to 0.2 mm is spirally wound around the outer periphery of a twisted expanded graphite base member 2 having a width of 3 mm and a thickness of 0.38 mm, at a narrow pitch P of 0.5 to 5 mm without slack. Alternatively, the reinforcing wire member is wound so as to be embedded in the inner side of and along an edge 4 of an expanded graphite tape which is spirally exposed from the outer surface of the expanded graphite base member 2.