PROBLEM TO BE SOLVED: To form a dug furrow at a vertical port passage formation position by a lower part of a plow member scooping mud in a field and discharging the mud to a side in travelling of a travel machine body, to form a plunged groove and a vertical port passage opened in the dug furrow, and thereby to suppress blocking of an opening of the plunged groove and vertical port passage by the mud on the field surface.SOLUTION: The culvert formation device includes: a bullet body 21 arranged in a lower part of a plunge beam 9 and capable of forming a culvert H； an expansion member 22 capable of forming a vertical port passage T opened on a ground surface M by expanding a side face of a plunged groove S formed while extended in a vertical direction in field mud W by the plunge beam； a movement mechanism 8 moving a machine frame 5 in a right/left direction orthogonal to a travel direction of a travel machine body 1； a pivotal fitting mechanism 6 connecting the machine frame to the travel machine body so as to rotate horizontally； and a plow member 31 arranged on the machine frame and capable of forming a dug furrow U at a vertical port passage formation position D by scooping the field mud and discharging the mud to a side.SELECTED DRAWING: Figure 18
