The rotary blade A1 includes a holding member 100 attached to the rotary blade mounting shaft 14 of the mower and rotated, a holding member 100 which is held at the base end side by the holding member 100, and a tip end side of the rotary blade A1 is pulled out in a radially outward direction A guide member 200 which is rotatable relative to the holding member 100 with respect to the rotation axis centering on the holding member 100, a guide member 200 which is provided on the outer periphery of the guide member 200 and which is rotatable inward in the radial direction of the guide member 200 , And the concave portion 240 has a bottom portion 241, a first inclined portion 242 continuing from the bottom portion 241 to the front side in the rotation direction of the holding member 100, and a plurality of concave portions 240 extending from the bottom portion 241 to the holding member 100 And a second inclined portion 243 continuing to the rear side in the rotation direction of the guide member 100. The first inclined portion 242 has a first inclination angle with respect to the radial direction r of the guide member 1001Of the second inclined portion 243 relative to the radial direction r of the guide member 2002It is larger than.回転刃A1は、草刈機の回転刃取付け軸14に取付けられて回転させられる保持部材100と、保持部材100に基端側が保持され、先端側が半径方向外方に導出させられたコード状切断部材4aと、保持部材100の下位において保持部材100に対してその回転軸心を中心として相対回転可能なガイド部材200と、ガイド部材200の外周に設けられ、それぞれがガイド部材200の半径方向内方に凹入する複数の凹部240と、を備えており、凹部240は、その底部241と、底部241から保持部材100の回転方向前方側に続く第1傾斜部242と、底部241から保持部材100の回転方向後方側に続く第2傾斜部243とを含んでおり、第1傾斜部242のガイド部材100の半径方向rに対する第1傾斜角度θ1は、第2傾斜部243のガイド部材200の半径方向rに対する第2傾斜角度θ2よりも大である。
