Abstract: The present invention is concerned with a cleavage type safety valve installed on a metal vessel for affording the explosion-proof function. The safety valve is installed on a small-sized cell vessel which remains hermetically sealed during the normal operation but instantly releases the pressure in the inside of the vessel if, due to abnormalities, such as overcharging, the pressure is increased and reaches a prescribed value to prevent explosion or deformation of the cell vessel. The metal foil type safety valve by the cold pressure welding of the present invention cold welds the metal foil for sealing the air vent hole in the metal vessel. If the internal pressure in the vessel reaches the prescribed value, the metal foil is cleft to form an opening in the vessel to release the internal pressure.