the present invention relates an enclosed cell and fabricating methods of the cell which has a safety valve mechanism for releasing gas from inside the cell when an internal pressure of the cell rises to an excessive degree . the characterizing feature of the invention resides in the use of a resin packing as sealing element , junctions between the resin packing and a metal lid and between the resin packing and a polar terminal being closed tight by thermal fusion . this construction assures reliable sealing in normal state , and permits the packing to break with an excessive rise in the internal pressure thereby to release gas from inside the cell . the cell of this invention is readily fabricated by injection molding or by a hot press process . therefore , the enclosed cell according to this invention is fabricated very rationally and inexpensively , assures excellent sealing and safety , and has wide application .