A forming system that forms a metal pipe from a cylindrical metal pipe material having a welded portion in which end portions of a plate material are welded to each other, the forming system comprising: a forming apparatus which includes a set of dies , and a heating and expanding part which heats the metal pipe material disposed between the set of dies and supplies a gas into the metal pipe material to expand the metal pipe material ; characterized in that the forming system further comprises: a supply device which rotates the metal pipe material around a central axis of the metal pipe material and supplies the metal pipe material to the forming apparatus ; a position detection unit which detects a direction in which the welded portion is located with respect to a center of the metal pipe material in a case of being viewed from an extension direction, before the metal pipe material is supplied to the forming apparatus by the supply device ; and a control device which includes a storage unit and a control unit and controls an operation of the supply device , wherein in a case where a position at which a distance from the center of the metal pipe material is the longest, on a surface of any one of the dies of the set of dies , in a space which is formed by the cavity of the set of dies , in a case of being viewed from the extension direction of the metal pipe material in a state where the metal pipe material is disposed between the set of dies , is set to be a longest position (R1), the storage unit stores information on the longest position (R1), and the control unit controls, based on the information on the longest position (R1) stored in the storage unit , a supply of the metal pipe material to the forming apparatus by the supply device such that the welded portion is not located on a straight line connecting the longest position (R1) and the center of the metal pipe material . a supply device which rotates the metal pipe material around a central axis of the metal pipe material and supplies the metal pipe material to the forming apparatus ; a position detection unit which detects a direction in which the welded portion is located with respect to a center of the metal pipe material in a case of being viewed from an extension direction, before the metal pipe material is supplied to the forming apparatus by the supply device ; and a control device which includes a storage unit and a control unit and controls an operation of the supply device , wherein in a case where a position at which a distance from the center of the metal pipe material is the longest, on a surface of any one of the dies of the set of dies , in a space which is formed by the cavity of the set of dies , in a case of being viewed from the extension direction of the metal pipe material in a state where the metal pipe material is disposed between the set of dies , is set to be a longest position (R1), the storage unit stores information on the longest position (R1), and the control unit controls, based on the information on the longest position (R1) stored in the storage unit , a supply of the metal pipe material to the forming apparatus by the supply device such that the welded portion is not located on a straight line connecting the longest position (R1) and the center of the metal pipe material . <EOS>