The construction method of retaining wall

A construction method of an underground retaining wall using a non-supporting formwork system is provided to shorten construction progress and to heighten constructability and solidity by constructing a retaining wall by fixing a form to a form supporting coupler welded to an H-beam built in a CIP or SCW wall using a connecting rod, not using supports for supporting a form. A construction method of an underground retaining wall using a non-supporting formwork system comprises the steps of: constructing CIP(Cast In Place) or SCW(Soil Cement Wall) piles to the appointed site for constructing an underground structure, and excavating under the ground; chipping to make one side of a flange of an H-beam(H) built in a CIP or SCW underground continuous wall exposed, and welding a stud bolt and a form supporting coupler(22) to the exposed side of the flange of the H-beam; arranging reinforcing bars for an underground retaining wall, and fastening a connecting rod(40) to the form supporting coupler; fastening a form(50) to the end of the connecting rod; placing concrete to a space between the CIP or SCW and the form; and hardening the concrete and removing the form.