PURPOSE: To shorten the construction period for setting a steel tubular sheet pile by a method in which a steel tubular sheet pile cell is made up by assembling plural steel tubular sheet piles into a round flat shape, and then the steel tubular sheet pile cell is towed to the sea and settled in place.

CONSTITUTION: In the first place, a steel tubular sheet pile cell is made up by connecting plural steel tubular sheet piles 1 by using a tool 3 through cuplers 2 vertically fixed to each steel sheet pile 1 into a round flat shape. Then, a floating rubber device 5 is charged into each steel tubular sheet pile of said cell. The floating rubber device 5 consists of expansions 51 to be expanded and pressed at both internal ends of each steel sheet pile 1, a coupling portion 52, and a clamping portion 53. The cell fitted with the rubber device 5 is towed to a settling place on the sea 7 and then settled gradually by removing compressed air in the expansion 51 of the rubber device 5. Afterwards, a vibro-pile driver is set on the upside of the cell and each sheet pile 1 is driven into the sea bed.