PROBLEM TO BE SOLVED: To continuously form a vertical port passage by continuously steering and driving a traveling machine body, thereby improving working efficiency, improving drainability and air-permeability of the farm field by forming a continuous penetration mark groove, and improving safety by holding a no-load position of the machine frame in a direct advance direction while forming a non-vertical passage and the like.SOLUTION: An expansion member 15 is arranged in a machine frame 4, which can form a vertical port passage T opening in a ground surface M by expanding side surfaces of a penetration mark groove S extendingly formed in the vertical direction in soil W with a penetration beam 6, an expansion mechanism 16 is provided, for forcing the expansion member to perform an expansion movement R, the machine frame is joined to an attachment frame 3 with a pivotally-fitting mechanism 5 so as to enable a horizontal rotation E, and a position holding mechanism 25 is provided, which can hold a no-load position of the machine frame in a direct advance direction of a traveling machine body 1.
