Abstract: A pipe coupling inc1udes a pair of half members which have a half-ring shape on the x-y plane and a thickness along the z axis, wherein the half member includes a first end on which a circumferential groove is disposed, the circumferential groove including a first groove surface and a second groove surface which are inclined over the x-y plane; and a second end on which a circumferential protrusion is disposed, the circumferential protrusion including a first protrusion surface and a second protrusion surface which are inclined over the x-y plane, wherein the first groove surface and the second groove surface are inclined over the x-z plane in the same angle and direction as the first protrusion surface and the second protrusion surface.