A die includes a first die and a second die, and at least one of the first die or the second die includes: a bottom portion having a plate shape; a top portion having a plate shape and is provided apart from the bottom portion; and a stiffening member having one end directly connected to the bottom portion and another end connected to the top portion, the stiffening member extending in an inclined manner from a connection portion with the bottom portion toward a side at which a center of the top portion is located as the stiffening member extends from the bottom portion side toward the top portion side.