A lawn mower including an engine having an output shaft, an air impeller, a plurality of cutter blades, and a driven shaft having the air impeller and the cutter blades connected thereto. The driven shaft is connected to the output shaft of the engine through a centrifugal clutch having a drum, and a brake band is located in a path of air drawn by suction by the air impeller for clamping against the outer periphery of the drum of the centrifugal clutch to interrupt rotation of the driven shaft.