A lawn mower having upper and lower cutter blades (15, 14) in a cutter housing (12) is disclosed. The blades are disposed with a phase difference such that upper blade edge parts (122, 122) of the upper cutter blade (15) are advanced forward with respect to lower blade edges (38, 38) of the lower cutter blade (14) in the rotation direction, whereby interference of the upper cutter blade with the air-lifting parts (39, 39) of the lower cutter blade is avoided, and the noise produced by the rotation of the upper and lower cutter blades is reduced.
