To obtain a connected structure of three-dimensional network which can expands the three-dimensional network to a desired area and has excellent strength at their junctions.

In the production of a three-dimensional network which is formed by allowing a plurality of loop filaments made of a synthetic resin to irregularly interlaceing to each other and fusing the filaments mutually at their interlacing points, at least one end of each three-dimensional network 1 is made more densified and thinner 2 in its loop filaments than those in the main body 2 and a plurality of three-dimensional networks 1 are connected through the thinned parts 3.