PURPOSE: To construct a column which has an uniform strength, by a method wherein the screw part of an adjoining rotary longitudinal shaft is positioned between the screw part and the screw part of a rotary longitudinal shaft, and the rotation traces of the screws of the adjoining shafts are partially overlapped with each other.

CONSTITUTION: With a rotary device 1 turned, rotary longitudinal shafts 2 are spun, and the ground is excavated as an earth and sand solidifying solution is jetted through the bit at the end of the rotary longitudinal shaft. The excavated earth and sand is elevated up to a given extent as it is mixed and egitated with the solidifying solution by the screw parts of the rotary longitudinal shafts 2, the excavated earth and sand, mixed with the solution further elevated up to a given extent, is further elevated up to a given degree as the mixture is further uniformly mixed and agitated by the screw part of the adjoining rotary longitudinal shaft, the similar process is repeated in the followings. The turn traces of the screw parts 3 attached to the adjoining rotary longitudinal shafts 2 are partially overlapped, which causes the mixed earth and sand to smoothly move from the screw part to the adjacent screw part.