2. A three-dimensional netted struc

2. A three-dimensional netted structure having an upper surface, a lower surface, two side surfaces, a left end surface, and a right end surface, said structure comprising a plurality of filaments helically and randomly entangled and thermally bonded together, wherein:said filaments are formed out of a thermoplastic resin by extrusion molding followed by cooling in a liquid;said structure is four-surface molded, the upper surface, the lower surface and the two side surfaces being molded;said structure has a first pattern of sparse and dense portions arranged alternately in a direction that is perpendicular to a direction in which the thermoplastic resin is extruded wherein said structure has a single or multiple beam-like high-density regions arranged in a direction of thickness of said structure;said structure has a second pattern of sparse and dense portions wherein all surfaces of an outer peripheral region of said structure that are in parallel to the direction in which the thermoplastic resin is extruded have a higher density than a density of remaining portions of said structure; andsaid first pattern of sparse and dense portions and said second pattern of sparse and dense portions are formed by cooling in a liquid.