In a state in which an arm 21 is oscillated to a lowest position, each control link 22 is arranged to be horizontally extended backward where the control link 22 is pivotally connected to a point A, and is pivotally connected to the arm 21 at a point D. An arm cylinder 23 is arranged to be vertically extended upward where the arm cylinder 23 is pivotally connected to a point B, and is pivotally connected to the arm 21 at a point E. The lift link 24 is arranged to be vertically extended upward where the lift link 24 is pivotally connected to a point C, and is pivotally connected to the arm 21 at a point F. The points E and F are located above the point D.