By the control of a controller, a gas is supplied into a metal pipe material from a gas supply part so as to expand a part of the metal pipe material in sub-cavity parts, and then a driving mechanism is driven such that expanded parts of the metal pipe material are pressed by an upper die and a lower die to form flange parts. In addition, by the control of the controller, a gas is supplied into the metal pipe material after the formation of the flange parts from the gas supply part so as to form a pipe part in a main cavity part. In this manner, the controller controls the gas supply part and the driving mechanism, and thus flange parts and a pipe part having a desired shape can be easily formed.