A cutter housing for use in a power-driven lawn mower has a substantially cylindrical skirt wall and a top wall covering the upper end of the skirt wall. The top wall has a substantially central recess for accomodating the engine of the lawn mower and includes a pair of half members positioned one on each side of the recess and lying substantially flush with each other in symmetrical and contiguous relation. The cutter housing also has a rear housing portion extending rearwardly in contiguous relation to the skirt wall and the top wall, and a partition disposed in the rear housing portion and dividing the rear housing portion into two spaces. The skirt wall, the top wall, the rear housing portion, and the partition are integrally molded of synthetic resin.