PROBLEM TO BE SOLVED: To provide the subject unit which can change an angle for attaching cutting members to selectively use plural blade sides, cut plants also from the vertical direction, and also cut firm various trees. SOLUTION: Blade sides divided into plural sections are formed on the outer peripheral edge of each cutter member in the rotary cutting unit of a plant cutting machine, and an angle for attaching the cutter member to a rotor can be changed to direct one or more arbitrary blade sides in a cutting direction. The cutter member is attached so as to give a cutting blade side that an arbitrary blade side is approximately radially disposed on the rotation axis of the rotor, and angular portions are formed at the sections of the blade sides, respectively. The cutting blade sides of the cutter member are attached in a downward tilted state toward the rotation travel of the cutting unit.
