The present invention relates to a cap for a VRLA battery which discharges gas produced in a VRLA battery through a simple structure, and blocks introduction of external air to adjust the internal pressure of the battery. According to an embodiment of the present invention, the cap for a VRLA battery comprises: a head to cover an outlet formed on a battery cover; a body formed on a bottom portion of the head, inserted and mounted in the outlet, and provided with a vent hole which is formed on a side of an upper portion thereof and communicates with an inlet hole formed on a lower portion thereof; a fastening unit extended from the body and inserted into the outlet to tightly attach and fix the body on the battery cover; a first sealing member which surrounds the vent hole, is elastically deformed to be opened if a gas pressure in a battery is higher than or equal to a prescribed pressure, and is closed by an elastic force of the same; and a second sealing member placed on a protrusion formed on a side of the lower portion of the body and tightly attached to an inner surface of the battery to prevent a leakage of gas to the outside.
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