The present invention relates to a storage-battery vent cap which adjusts an internal pressure of a storage battery by exhausting a gas generated inside the storage battery to the outside and blocking inflow of external air. The vent cap includes a cylindrical body installed in a vent hole of the battery and formed with an exhaust hole; a cylindrical insert coupled to the body, a partition being formed inside the insert and a coupling hole and a air vent being formed in the partition; and a valve fixed to the coupling hole and elastically deformed by an internal pressure of the battery to open the air vent. The valve has an umbrella-like shape including a valve body having a larger diameter than that of the coupling hole, a cover formed on an outer circumferential surface of the valve body, and a fixing portion downwardly protruded from the valve body.