In a mower provided with a center pivot axle 12, a control unit 1 controls a height adjusting mechanism 19 for a mowing unit 16 so that a grass cutting height is increased from an initial level when an absolute value of a roll angle of the center pivot axle relative to a vehicle body has exceeded a first roll angle threshold value. A cutting blade 21 is stopped when the absolute value of the roll angle has exceeded a fourth roll angle threshold value which is greater than the first roll angle threshold value.
