NOVELTY - A metal microparticles-dispersed composite (10) comprises a matrix layer (1) having solid backbone portions (1a) and voids (1b) formed by the solid backbone portions, and metal microparticles (3) which are fixed on the solid backbone portions of the matrix layer. The solid backbone portions comprise an aluminum oxyhydroxide or alumina hydrate, and form a three-dimensional network structure. The metal microparticles have average particle diameter of 3-100 nm. The content of metal microparticles having particle diameter of 1-100 nm, is 60% or more.    USE - Metal microparticles-dispersed composite is used for substrate for generating localized surface plasmon resonance (claimed) used for electrode of fuel cell, air cell, water-electrolysis apparatus, electrical double layer capacitor, gas sensor, exhaust pollution removal apparatus and electronic device, and used as catalyst.    ADVANTAGE - The metal microparticles-dispersed composite has excellent localized surface plasmon effect and structural characteristics.    DETAILED DESCRIPTION - A metal microparticles-dispersed composite comprises a matrix layer having solid backbone portions and voids formed by the solid backbone portions, and metal microparticles which are fixed on the solid backbone portions of the matrix layer. The solid backbone portions comprise an aluminum oxyhydroxide or alumina hydrate, and form a three-dimensional network structure. The metal microparticles have average particle diameter of 3-100 nm. The content of metal microparticles having particle diameter of 1-100 nm, is 60% or more. The metal microparticles exist in such a manner that the metal microparticles are not in contact with one another and any two adjacent metal microparticles are apart from each other by a distance which is equal to or more than the particle diameter (DL) of one of the two adjacent metal microparticles which has a larger particle diameter (D) than that of the other one. Each of the metal microparticles has a portion which is exposed to the voids of the matrix layer, and the metal microparticles exist in a state dispersed three-dimensionally in the matrix layer. INDEPENDENT CLAIMS are included for the following:    (1) localized surface plasmon resonance-generating substrate; and    (2) manufacture of metal microparticles-dispersed composite.    DESCRIPTION OF DRAWING(S) - The drawing shows schematic view of metal microparticles-dispersed composite.    Matrix layer (1)    Solid backbone portions (1a)    Voids (1b)    Metal microparticles (3)    Metal microparticles-dispersed composite (10)