To provide a green lawn mower of walk-behind type, including a mobile structure and a ground traction member which is rotatably connected to the mobile structure and tracks and moves the mobile structure on the ground.

In this green lawn mower, an internal-combustion engine 32 is supported by the mobile structure 40 and outputs driving force to an output shaft 48. A bed knife is supported by the mobile structure having a cutting edge and cooperates with a lawn-mowing reel 18 which is rotatably supported on the mobile structure. The lawn-mowing reel includes cutting blades 20 which cut grass by associating with the bed knife. A drive system 38 is operatively connected to the output shaft 48 and at least any one of the ground traction member and the lawn-mowing reel 18, by being positioned between them, and transmits the driving force to them. The drive system includes a centrifugal clutch member which is joined to the output shaft 48. The centrifugal clutch member does not transmit the driving force to the ground traction member, nor to the lawn-mowing reel, before the output shaft reaches a prescribed rotational speed, and therefore a complicated interlocking mechanism is not required.