Abstract: It is an object of the present invention to improve reliability of a battery cell by preventing residual stress in the ting of a sealing gasket so as to provide a sealing gasket which does not crack. The object is achieved by a sealing gasket for a battery cell produced by injecting molten resin into a cavity from a gate which corresponds to a tip of a resin injection nozzle of a metal mold, wherein a ring forming a body of the gasket has an inward protrusion projecting inwardly from an internal surface of the ring and the gate is operatively disposed at a part which corresponds to the inward protrusion. In the sealing gasket so-produced, residual stress is generated in the inward protrusion. Therefore, the strength of the ring does not deteriorate because of the effects of the residual stress and cracking of the gasket can be prevented.