An energy storage element includes: a container; an electrode assembly housed in the container; an electrode terminal; a current collector which electrically connects the electrode terminal and the electrode assembly; and an external insulation sealing member for insulating the container and the electrode terminal. The container includes a protrusion part having a through-hole for allowing penetration of the electrode terminal and protruding from the upper surface of the container. The electrode terminal is electrically connected to the current collector in a state where the electrode terminal penetrates through the protrusion part. The external insulation sealing member has a side part disposed along the side surface of the protrusion part, and the end surface of the end part of the side part at the side of the upper surface is apart from the upper surface.