Abstract: The occurrence of micro-crack is prevented at the root of a thermally sealed area of casing materials even if a thick electric device element is sealed. Film covered battery 10 has cell element 13 to which leads 12a, 12b are connected, and casing films 11 for sealing cell element 13 with leads 12a, 12b extended therefrom. Casing films 11 are thermally sealed along the periphery to seal cell element 13. Thermally sealed area 13 of casing films 11 is positioned between both surfaces of cell element 13 in the thickness direction of cell element 13. On a side of casing films 11 from which leads 12a, 12b are not extended, close contact zone 15, in which casing films 11 are not thermally sealed to each other but are in close contact with each other, is formed continuously to a space which receives cell element 13. Close contact zone 15 has a length of one-half or more of the distance from one end to the other end of an inner edge of thermally sealed area 14.