A valve structural body that is easy to attach to a container is for a power storage device, and includes a casing in which a passage through which gas generated inside of the container is discharged to the outside of the container is formed, and a valve mechanism that is accommodated in the casing and allows the gas to pass through the passage to the outside of the container via the passage if the internal pressure of the container has risen due to the gas generated inside of the container. The casing includes a first plane, and a second plane that is parallel to the first plane.