In a lawn mower provided with a lawn mowing mechanism (13), a grass collection box (18) receiving grass mowed by the lawn mowing mechanism, a lift mechanism (19) for lifting up the grass collection box (18) high, and a rear lid plate (21) structured such as to openably close an opening in a rear surface of the grass collection box (18), the invention achieves an improvement of a stability of a support at a time of lifting up the grass collection box (18) high in the case of discharging the mowed grass in the grass collection box (18) in a state of lifting up the grass collection box (18) high, and also achieves a downsizing and a weight saving. A bottom portion of the grass collection box (18) is opened, the opened bottom portion is openably closed by a bottom lid plate (20), and the mowed grass is discharged from the grass collection box (18) by an opening actuation of the bottom lid plate (20) and the rear lid plate (21).
