PROBLEM TO BE SOLVED: To continuously form a vertical port passage by continuously steering and driving a traveling machine body even near an inner peripheral corner part of a field surface, without stopping the traveling body or raising or lowering an attachment frame or machine frame in a stopped state, thereby improving working efficiency and improving drainability and air-permeability of the farm field by forming a continuous penetration mark groove.SOLUTION: An attachment frame 3 is joined to a traveling machine body 1 by using a joint mechanism 2, a machine frame 4 is joined to the attachment frame, a penetration beam 6 is vertically attached to the machine frame so as to enable a swing movement D in an advance direction, a swinging mechanism 7 for swinging the penetration beam is provided, an expansion member 15 is arranged on the machine frame, 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 the penetration beam, an expansion mechanism 16 is provided, for forcing the expansion member to perform an expansion movement R, and the machine frame is joined to the attachment frame with a pivotally-fitting mechanism 5 so as to enable a horizontal rotation E.
