A riding mower having left and right driving rear wheels independently drivable forward and backward and a pair of left and right steerable front wheels is provided with a support device capable of being mounted with a cylindrical gas cylinder in a horizontal position on an external side of a rollover projection frame. The support device is provided such that the mounted gas cylinder is positioned along front and rear of the rollover protection frame and is mounted in a tilted state in which the central axis of the cylindrical gas cylinder is closer to a central side in a lateral direction of a vehicle body toward a rear side from a plan view.