A mower tractor includes a vehicle body supported by a plurality of wheels; an engine mounted to the vehicle body; a mower suspended from the vehicle body; at least one grass collector bag for collecting grass cut by the mower; a grass collector bag holder supporting said at least one grass collector bag at a position on one side with respect to the engine; and a stopper portion for abutting against the grass collector bag so as to prevent the grass collector bag supported by the grass collector bag holder from moving toward the vehicle body.