SEALING PLATE

A sealing plate including an explosion-proof valve whose opening pressure can be set easily, and whose groove will not be not ruptured by a repeated stress before reaching an opening pressure. The explosion-proof valve including a thin plate portion thinner than a plate; a valve portion formed by partially projecting the thin plate portion in a thickness direction to enhance a bending rigidity; and a groove drawn as a boundary between the valve portion and the thin plate portion to serves as a score line. A rupturable portion that is ruptured after the groove is ruptured is formed between a straight line and a folding line. The valve portion is bent along the folding line to open the explosion-proof valve when the rupturable portion is ruptured after the groove is ruptured.