To control the traveling speed of a paddy field traveling sulky working machine in the case of moving the machine into or out of a field by operating an operation tool operable out of the machine in place of operating a speed changing lever operable only on the driver's seat.

The output of an engine is transmitted to a mission case-side transmission shaft 18 with a belt speed changer 16 having a tension applying means 24. A speed changing lever 35 to operate the belt speed changer 16 is made to be operable from the driver's seat. An operation tool 46 to operate the belt speed changer 16 is placed at a position separated from the speed changing lever 35 and operable at a position out of the machine.