A blade mounting structure (20) of a lawn mower (10) includes a blade holder (21 70 80 90) including a shaft-mounted section (31) connected to an output shaft (16) of an engine (15), and a blade mounting section (33) having a grass cutting blade (22) mounted thereto. The blade holder (21 70 80 90) further includes a connecting leg section (35 72 82 92) located between the shaft-mounted section (31) and the blade mounting section (33) and interconnecting the shaft-mounted section and the blade mounting section. The connecting leg section (35 72 82 92) has a wall thickness dimension gradually decreasing in a direction from the shaft-mounted section toward the blade mounting section.
