A forming system includes: a forming apparatus which supplies gas into a cylindrical metal pipe material having a welded portion to expand the metal pipe material; a supply device for supplying the metal pipe material to the forming apparatus; and a control device for controlling an operation of the supply device, in which in a case where a position where a distance from a center of the metal pipe material is the longest, on a surface of the die, when viewed from an extension direction of the metal pipe material in a state where the metal pipe material is disposed between the dies, is a longest position, the control device includes a control unit which controls supply of the metal pipe material to the forming apparatus such that the welded portion is not located on a straight line connecting the longest position and the center of the metal pipe material.