[Summary] A mower unit includes an idler pulley unit and a single belt routed around an output pulley of a drive source, the idler pulley unit and a plurality of blade pulleys. The idler pulley unit includes a first idler pulley, a second idler pulley and a tension idler pulley. A pulley height of the idler pulley unit is set higher than a pulley height of the blade pulleys, and a forward belt portion from the output pulley and a reverse belt portion to the output pulley extend to pass over and above the blade belt portion.