A method of simultaneously manufacturing a plurality of three-dimensional randomly looped structures, the method comprising: a. extruding a plurality of assemblies of filaments (21a and 21b) from melted thermoplastic resin across a predetermined interval through a nozzle having hole groups (32a and 32b) and a hole-free region formed between the hole groups, each hole group comprising multiple rows of holes, each row of holes comprising a plurality of holes, such that the assemblies of filaments of the plurality of assemblies of filaments extruded from the hole groups are spatially separated from one another by the hole-free region and fall downwardly; b. passing the plurality of assemblies of filaments between a pair of first chutes (4a and 4b) and a second chute, wherein the pair of first chutes is arranged to face one another across a space and is downwardly inclined toward the plurality of assemblies of filaments and a flow of water is provided on the pair of first chutes and the second chute, and wherein the plurality of assemblies is brought into contact with the flow of water to tangle and thermally fuse the plurality of assemblies of filaments irregularly, so as to form loops; and c. hauling off the plurality of assemblies of filaments at a lower rate than a rate at which the plurality of assemblies of filaments falls with a pair of haul-off machines (8a and 8b) arranged below the nozzle, and submerging the plurality of assemblies of filaments in water to cause the plurality of assemblies of filaments to cool down and solidify, such that the assemblies of filaments of the plurality of assemblies of filaments are spaced from one another when reaching a water surface of the water, whereby the assemblies of filaments are positioned adjacent to one another and are in contact with one another as the assemblies of filaments move between the pair of haul-off machines and are then separated from one another after passing through the haul-off machines, such that the plurality of three-dimensional randomly-looped structures (10a and 10b) corresponding to the plurality of assemblies of filaments is obtained. a. extruding a plurality of assemblies of filaments (21a and 21b) from melted thermoplastic resin across a predetermined interval through a nozzle having hole groups (32a and 32b) and a hole-free region formed between the hole groups, each hole group comprising multiple rows of holes, each row of holes comprising a plurality of holes, such that the assemblies of filaments of the plurality of assemblies of filaments extruded from the hole groups are spatially separated from one another by the hole-free region and fall downwardly; b. passing the plurality of assemblies of filaments between a pair of first chutes (4a and 4b) and a second chute, wherein the pair of first chutes is arranged to face one another across a space and is downwardly inclined toward the plurality of assemblies of filaments and a flow of water is provided on the pair of first chutes and the second chute, and wherein the plurality of assemblies is brought into contact with the flow of water to tangle and thermally fuse the plurality of assemblies of filaments irregularly, so as to form loops; and c. hauling off the plurality of assemblies of filaments at a lower rate than a rate at which the plurality of assemblies of filaments falls with a pair of haul-off machines (8a and 8b) arranged below the nozzle, and submerging the plurality of assemblies of filaments in water to cause the plurality of assemblies of filaments to cool down and solidify, such that the assemblies of filaments of the plurality of assemblies of filaments are spaced from one another when reaching a water surface of the water, whereby the assemblies of filaments are positioned adjacent to one another and are in contact with one another as the assemblies of filaments move between the pair of haul-off machines and are then separated from one another after passing through the haul-off machines, such that the plurality of three-dimensional randomly-looped structures (10a and 10b) corresponding to the plurality of assemblies of filaments is obtained.