To efficiently form a cut-off ditch to cut off ground vibration inside an underground continuos wall.

An underground wall 1 made by mixing and stirring original position soil and a solidifying material is constructed along at specified depth of a ground to cut off ground vibration to propagate in the neighborhood of a ground surface toward an environment from a hypocenter. A ground surface vibration cut-off ditch 10 extending along the wall body extending direction of the underground wall 1 is placed by inserting a mold material 11 in a wall body along the wall body extending direction while hardening of the wall body of the underground wall 1 progresses. The mold material 11 is extracted at a stage when the wall body is sufficiently hardened. At that time, a ditch space formed as the mold material 11 is removed is made as the ground surface vibration cut-off ditch 10.