A forming device that expands a metal pipe material to form a metal pipe includes a die that has an upper die and a lower die, at least one of which is movable, and that form the metal pipe, an electrode that energizes the metal pipe material to heat the metal pipe material, a gas supply part that supplies a gas into the heated metal pipe material to expand the metal pipe material, and a die movement suppressing part that suppresses the movement of the die by an electromagnetic force at least when the energization to the metal pipe material is performed by the electrode.