PURPOSE: To perform the smooth start of a machine body and to reduce fuel consumption and the generation of noise by suppressing an output to the minimum limit in an idling condition.

CONSTITUTION: A hand acceleration lever 16 with which an operation tool 15 for governing an engine energized for return to the idling side if brought into contact for operation is arranged in an arbitrary set position in a manner to effect frictional holding. A governing operation tool 19 interlocked and coupled with the operation tool 15 and the shift operation tool 22 of a continuously variable transmission 3 located in a machine body running drive system are arranged in juxtaposition in a manner to approach each other. An operation pedal 23 with which the operation tools 19 and 22 are brought into simultaneous contact for operation is provided. In the return position of the operation pedal 23, the governing operation tool 19, which is in an idling return state, and the operation pedal 23 are brought into approximate contact with each other, and a gap S for a given operation margin is provided between the shift operation tool 22 and the operation pedal 23.