PROBLEM TO BE SOLVED: To provide a spiral rotor which can ensure its straight traveling property when a control machine travels forward, and can suppress deterioration of working efficiency of grass cutting work by cutting lying grass and the like.SOLUTION: A spiral rotor 20 includes a rotation center shaft 31 connected to an axle of a control machine, an inner support member 22 and an outer support member 27 installed on axial both sides of the rotation center shaft 31 and along planes approximately orthogonal to the axial direction of the rotation center shaft 31, and a spiral blade 33 connected between these support members, and rotates in accordance with the rotation of the axle. The outer support member 27 includes a disk part 27a connected to the rotation center shaft 31, and a plurality of projecting plate parts 27b radially extending from the outer edge of the disk part 27a and formed at intervals in the circumferential direction. One end in the longitudinal direction of the spiral blade 33 is connected to the front side in the rotational direction of a tip of the projecting plate part 27b, and a longitudinal lug 27c extending along the rotational direction and projecting to the radial outside is installed on the rear side in the rotational direction of the tip of the projecting plate part 27b.
