To quietly and effectively drive an engine to perform efficient work by surely reducing the rotational frequency of the engine in a low working speed at traveling or the like or in a stop state of a working vehicle such as a planting machine in which a speed change gear for changing working speed such as vehicle speed is driven by the output of the engine.

The working vehicle is provided with the speed change gear 48 which is driven by the output of the engine 2 to change the working speed, and a working speed operating member 30 for performing the speed changing operation of the speed change gear 48 is interlocked with an engine rotation changing member 87 for changing the rotational frequency of the engine 2 through an interlocking member 88.