A metal assembled body including a first member formed by forging a metal material, the first member including a peripheral wall portion in which a metal flow is formed along an axial direction and an extending portion extending from the peripheral wall portion and having an opening, the peripheral wall portion and the extending portion being formed integrally, and a closing member welded to a welding surface on the extending portion to close the opening, before the closing member is welded, the extending portion being formed to expose an end portion of the metal flow at the welding surface, and a welding position of the closing member on the welding surface being set to make a width of a first region larger than a width of a region excluding the first region, the first region being a region divided by a welding site, where arrival of a gas is inhibited.