A spherical annular seal member 46 includes a spherical annular base member 42 defined by a cylindrical inner surface 38, a partially convex spherical surface 39, and large- and small-diameter side annular end faces 40 and 41 of the partially convex spherical surface 39; a plurality of partially convex spherical intermediate layers 43 formed integrally on the partially convex spherical surface 39 of the spherical annular base member 42 and laminated in a radial direction; and an outer layer 45 formed integrally on a partially convex spherical surface 44 of the outermost partially convex spherical intermediate layer 43 of these partially convex spherical intermediate layers 43.