A sole structure is provided that can improve cushioning and bending properties of the sole heel portion. The sole assembly 1 is formed of an upper plate 2 disposed on the upper side of the heel portion H, a wavy lower plate 3 provided below the upper plate 2 in the heel portion H and having at least two convex portions 30, 31 that protrude downwardly and that are adapted to form voids C relative to the upper plate 2, and a plurality of cleats that are provided on the lower surfaces of the convex portions of the lower plate and/or a cleat that is provided between adjacent convex portions of the lower plate.