TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Layer: The sealing material layer consists of layer (I) covering one surface of the solar cell element, and layer (II) covering the other surface.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compounds: The hardening agent is hardening agent not having an aromatic ring in a molecule, and/or cationic polymerization initiator. The hardening agent not having an aromatic ring is fatty amine, alicyclic amine, aliphatic acid anhydride, and/or alicyclic acid anhydride. The cationic polymerization initiator is diazonium salt, iodonium salt, sulfonium salt, and/or phosphonium salt.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The mass ratio of cycloaliphatic epoxy resin and aliphatic epoxy resin is 10-90:90-10, preferably 30-70:70-30. Preferred Properties: The cured material of the composition has a glass transition temperature of 40 degrees C or less. The cured material of thickness 2 mm has a light transmittance of 85-100% with respect to a light of wavelength 450 nm. Preferred Components: The cycloaliphatic epoxy resin is resin obtained by oxidizing the double bond of a cyclic olefin, hydrogenated bisphenol-A epoxy resin, and/or hydrogenated bisphenol-F type epoxy resin. The diol and/or triol are polyether glycol, polycaprolactone polyol, and/or polycarbonate diol. EXAMPLE - A resin composition was prepared by mixing (in %mass) YX8034 (RTM: hydrogenated bisphenol-A epoxy resin having epoxy equivalent of 270 g/eq and a total chlorine content of 0.14 %mass) (50), diglycidyl ether (50) of polytetramethylene ether glycol obtained by reacting polytetramethylene ether glycol and epichlorohydrin having a number average molecular weight of 650, and having a viscosity of 173 mPa.second, an epoxy equivalent of 447 g/eq, and a total chlorine content of 0.15 %mass, MH-700 (RTM: anhydrous methyl hexahydrophthalic acid) (50), PX-4MP (RTM: quaternary phosphonium salt) (1), 2,6-di-t-butyl-p-cresol (0.2), triphenyl phosphite (0.2), and Hostavin VSU (RTM: oxalanilide) (0.2). The composition had viscosity of 310 mPa.second at 25 degrees C. The cured material of the composition had a Shore D hardness of 56, a Shore A hardness of 90, a glass transition temperature of 13 degrees C as measured by JIS-K6911, a light transmittance of 90% with respect to light of wavelength 450 nm, a bending strength of 5.1 MPa as measured by JIS-K6911, a bending elastic modulus of 141 MPa as measured by JIS-K6911, and a deflection amount of 7.6 mm.