A storage battery sealing member includes a vulcanized rubber composition; the rubber composition contains a silicone rubber and a vulcanizing agent; a hardness Ha of the sealing member at 23° C. and a relative humidity of 50%, is 90 points or less; a compression set of the sealing member, measured after 25% compression followed by aging at 150° C. for 70 hours, is 80% or less; a difference between the hardness Ha of the sealing member at 23° C. and the relative humidity of 50% and a hardness Hb of the sealing member at 23° C. and the relative humidity of 50% after heated at 400° C. for 10 minutes is within 15 points; and a mass of a residue after heating the sealing member at 800° C. for 5 minutes, relative to the sealing member before heating, is 70 to 100% by mass.