PROBLEM TO BE SOLVED: To provide a grass mower that includes a machine body travelling by a pair of right and left front wheels and by a pair of right and left rear wheels, and that can travel quickly and mows grasses quickly.SOLUTION: In the grass mower, an opening 94 for work is disposed at the lateral side wall portion of a mower blade housing 11 so as to be opened and closed by a lid body 95. When steering operation is done to make a pair of right and left front wheels 2 and a pair of right and left rear wheels 3 face in the same lateral direction and be in the same lateral steering condition, so as to laterally travel the travelling machine body with the opening 94 for work facing in the travelling direction.
