Abstract: A tree cutting device comprises two opposed curved knife blades, each defining a portion of a surface of revolution. Swingable arms for the curved knife blades are journalled on separate shafts which are arranged with their axes in a common plane inclined relative to the center line of the trees to be cut. The separate shafts are arranged at an angle to each other so that their axes intersect at a point between the journalling means for the arms and the intersection between the common plane for the axes of the shafts and the center line of the maximum diameter tree to be cut. Preferably, each knife blade defines a portion of a sphere. To assure proper guidance of the knives, the knife edge of each blade is located unsymmetrically relative to the thickness of the blade.