To provide a battery safety device which has a simple structure and can prevent variation of an operating pressure even if it is high.

The battery safety device is provided with a covering plate 24 which divides the battery into an inner part and an outer part and on an outer face 24a of which a degassing hole 28 with an opening end is formed, a rubber valve 30 arranged on an outer face 24a of the covering plate 24 to cover the opening end of the degassing hole 28, and a beveled face 34 which is formed on the opening end of the degassing hole and beveled toward the outer face 24a of the covering plate 24 from an inner circumferential face 28a of the degassing hole 28. Furthermore, the safety device is provided with a cathode terminal 32 disposed on the outer face 24a of the covering plate 24 and covering the valve 30. The valve 30 is compressed between the covering plate 24 and the cathode terminal and is pressed on the beveled face 34 and an area of the outer face 24a of the covering plate 24 surrounding the beveled face 34.

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