NOVELTY - A sealing material sheet comprises ethylene/( alpha )-olefin copolymer, organic peroxide and silane coupling agent, and satisfies specified relations (i) and (ii) with respect to theoretical amount of oxy radicals generated from one molecule of organic peroxide, molar quantity of organic peroxide, molar quantity of silane coupling agent, content (in parts mass) of organic peroxide with respect to 100 parts mass ethylene/( alpha )-olefin copolymer, and molecular weight of organic peroxide.    USE - Sealing material sheet is used for solar cell module (claimed).    ADVANTAGE - The sealing material layer formed using the sealing material sheet has excellent adhesiveness and high crosslinking density, and provides solar cell module having high reliability for a long period of time.    DETAILED DESCRIPTION - A sealing material sheet comprises ethylene/( alpha )-olefin copolymer, organic peroxide and silane coupling agent, and satisfies relations: 5.4 less than or equal to (Ax B)/C less than or equal to 10.1 (i), and 6x 10-3 less than or equal to Ax (D/E) less than or equal to 1x 10-2 (ii), where A is theoretical amount of oxy radicals generated from one molecule of organic peroxide, B is molar quantity of organic peroxide, C is molar quantity of silane coupling agent, D is content (in parts mass) of organic peroxide with respect to 100 parts mass ethylene/( alpha )-olefin copolymer, and E is molecular weight of organic peroxide. An INDEPENDENT CLAIM is included for solar cell module (5), which has a photovoltaic cell (3), a sealing material layer (2) which seals the photovoltaic cell, and a surface-protection component (1) which protects surface side of the sealing material layer. The sealing material layer is formed using the sealing material sheet.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the solar cell module.    Surface-protection component (1)    Sealing material layer (2)    Photovoltaic cell (3)    Back surface protection component (4)    Solar cell module (5)