To solve problems of a conventional rotatingly penetrating method for a steel pipe in which a blade having a screwing action on the ground such as a spiral blade is attached to the end or near the end of the steel pipe and the steel pipe is penetrated in the ground while the steel pipe is rotated wherein though the method is widely used, a steel pipe with a thickness sufficiently larger than the thickness required for the design must be used to prevent the steel pipe from being twisted off or bent since a large torque is applied to the steel pipe during the construction, and the cost of the steel materials is increased.

A rotary propelling blade body with an outer diameter larger than that of the steel pipe body is fixed coaxially to the bottom end of the cylindrical steel pipe body so that the opening thereof is closed, and detachably engaged with the bottom end of a rotating shaft to which a rotational force is provided. An engagement part for transmitting the torque from the rotating shaft to the rotary propelling blade body is provided to the rotary propelling blade body on the inner diameter side of the steel pipe body to configure the rotatingly penetrated steel pipe.