This undercoat foil for an energy storage device electrode comprises a collector base plate, and an undercoat layer formed on at least one surface of the collector base plate, the undercoat layer containing carbon nanotubes, and the coating amount per collector base plate surface being 0.1 g/m2 or less. Since this undercoat foil can be effectively welded by ultrasound, the use thereof allows a low-resistance energy storage device and a simple and effective production method therefor to be provided.