A composite sealing material to be installed in a sealing groove includes a first sealing member that is located on the outer peripheral side of the sealing groove and that is made of an elastic member; and a second sealing member that is located on the inner peripheral side of the sealing groove and that is made of a material harder than the first sealing member, wherein the first sealing member is provided with a crosswise protrusion formed projecting in a radial inner direction from a radial inner side of the almost central section of the thickness direction; the second sealing member is formed in an almost cross sectional C shape by flange portions and formed at the both ends and an inner wall portion in an almost linear shape for connecting the flange portions; and a space is ensured between the crosswise protrusion and the inner wall portion in an almost linear shape of the second sealing member in a state that the first sealing member and the second sealing member are assembled in an integrated manner.