Exhaust circulation lawnmower

An exhaust circulation lawnmower is disclosed in which.grass clippings are sent, along with carrier air, from a cutter housing (12) to a grass bag (24); the grass clippings are held in the grass bag; and the carrier air is returned to the cutter housing as exhaust. A surface area A 1 of a grass clippings discharge opening (54) and a surface area A 2 of a recirculation opening (61) have a relationship of A 2 ‰ {1 /(1- ²N) 0.5 } A 1 , where A 1 is the surface area of the grass clippings discharge opening (54) through which the grass clippings and carrier air are discharged from the cutter housing to the grass bag, A 2 is the surface area of the recirculation opening (61) through which the carrier air is recirculated from the grass bag to the cutter housing, N is the number of bends having an angle of ± degrees in the space between the grass clippings discharge opening and the recirculation opening, and ² is a pressure loss coefficient for each of the bends.