NOVELTY - A modified hydrogenated block copolymer is obtained by introducing an alkoxy silyl group into hydrogenated block copolymer obtained by hydrogenating 90% or more of block copolymer with respect to total unsaturated bonds. The block copolymer consists of polymer block (A) having an at least 2 repeating units derived from an aromatic vinyl compound as a main component, and polymer block (B) having an at least 1 repeating unit derived from linear conjugated diene compound as a main component. The weight ratio of polymer block (A) and polymer block (B) is 20:80-60:40.    USE - Modified hydrogenated block copolymer for sealing material used for sheet and multilayer sheet for sealing solar cell element (all claimed).    ADVANTAGE - The modified hydrogenated block copolymer exhibits low moisture absorption, is not hydrolyzable, and has favorable weather resistance, transparency, and flexibility, maintains strong adhesion to glass even after being exposed to a high-temperature, high-humidity environment for a long period of time, and can seal a solar-cell element without being subjected to a special water-impermeability treatment. The modified hydrogenated block copolymer is efficiently and easily manufactured. The solar cell element is prevented from generation of crack.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) manufacture of modified hydrogenated block copolymer, which involves reacting ethylenic unsaturated silane compound with hydrogenated block copolymer in the presence of organic peroxide;    (2) sealing material (3), which contains modified hydrogenated block copolymer;    (3) laminated sheet, which is obtained by laminating a sheet containing the sealing material, on one or both surfaces of a sheet consisting of resin composition containing polymers other than hydrogenated block copolymer, optical stabilizers, ultraviolet absorbers, and antioxidant;    (4) multilayer sheet, which has a layer (I) containing modified hydrogenated block copolymer and a layer (II) containing modified (co)polymer obtained by introducing alkoxy silyl group into (co)polymer obtained by polymerizing ethylene and/or 3-10C alpha -olefin, and having melting point of 90-140 degrees C; and    (5) sealing method of the solar cell element, which involves arranging layer (I) side of multilayer sheet on solar cell element such that a crystal system photovoltaic cell is contacted.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic sectional view of crystalline silicon solar cell module.    Transparent front substrate (1)    Solar cell element (2)    Sealing material (3)    Tab (4)    Back surface protection sheet (5)