An encapsulating material for solar cell containing an ethylene/α-olefin copolymer satisfying the following a1) and a2), and a specific peroxyketal having a 1-hour half-life temperature in a range of 100 to 135 degrees centigrade; the peroxyketal being contained in an amount of 0.1 to less than 0.8 weight parts relative to 100 weight parts of the ethylene/α-olefin copolymer. a1) the shore A hardness is from 60 to 85 as measured in accordance with ASTM D2240. a2) MFR is from 2 to 50 g/10 minutes as measured under the conditions of a temperature of 190 degrees centigrade and a load of 2.16 kg in accordance with ASTM D1238.