A technology for improving molding properties while minimizing curling after molding in a battery packaging material comprising a laminate that is provided with a barrier layer, a heat-sealable resin layer positioned on one surface side of the barrier layer, and a polyester film positioned on the other surface side of the barrier layer. This battery packaging material is configured from at least a laminate provided with a barrier layer, a heat-sealable resin layer positioned on one surface side of the barrier layer, and a polyester film positioned on the other surface side of the barrier layer. The birefringence of the polyester film is in the range of 0.016-0.056.