1. A three-dimensional netted structure comprising:a netted structure being manufactured by preparing a thermoplastic resin as a raw material or a main raw material; anda sheet which is included in an internal portion of said netted structure,wherein said sheet is formed in a wavy pattern and extends from one end to another end of said netted structure,wherein said resin is formed into a plurality of helically and randomly entangled, partly and thermally bonded filaments by extrusion molding,wherein said filaments are cooled with a liquid so as to obtain said netted structure which includes said sheet having a percentage of void of zero continuously in a material extruding direction, thereby forming said sheet into said wavy pattern in said netted structure in said material extruding direction, andwherein said netted structure is a three-dimensional plate type netted structure having an apparent density of 0.02 to 0.9 g/cm3.