To efficiently perform the tightening work of a mold by arranging a plurality of rod-shaped bodies in a perpendicular direction on the outer peripheral surface of the mold assembled to a desired shape with the prescribed intervals in the peripheral direction, and winding a strip body around the outer periphery of the rod-shaped body and tightening it.

A plurality of rod-shaped bodies 2 are arranged on the outer periphery of a columnar mold 1, and the columnar mold 1 is tightened by giving the tension by a strip body 3 to the rod-shaped bodies 2. The rod-shaped bodies 2 are wide enough to withstand the placing pressure of the concrete and the tightening pressure by the strip body 3, and are arranged along the perpendicular direction of the columnar mold on the outer peripheral surface of the assembled columnar mold 1 with the prescribed intervals in the circumferential direction. After the strip body 3 equipped with a tightening jig 31 is wound around the outer circumference of each rod-shaped body 2 along the circumferential direction of the columnar body 3, the strip body 3 is tightened to tighten the mold when the concrete is placed into the columnar mold 1. Each rod-shaped body 2 is arranged on the outer circumference of the columnar mold 1 with the prescribed intervals, and the uniform tightening force can be provided to the columnar mold 1, performing the sure tightening.