A work vehicle includes wheels and a mower unit that are driven by power from an engine, and a mower driving detecting section for detecting power transmission condition to the mower unit. An isochronous controlling section controls the engine in an isochronous control mode for maintaining an engine rotational speed at a predetermined fixed value, independently of an engine load. A droop controlling section controls the engine in a droop control mode for varying the engine rotational speed in dependence on the engine load. If power is transmitted to the mower unit, the isochronous control mode is selected.
