To improve the electric control, etc., for connecting/switching a turning continuously variable transmission to/from a power steering lever in a traveling transmission case.

In the traveling transmission case 3, the power of two systems, i.e., a vehicle speed follow-up power system S for transmitting the output from an engine 4 after passing a sub transmission unit V by the drive of a traveling continuously variable transmission 5 and a fixed rotational power system F for directly transmitting the output from the engine 4 is selectively input to the turning continuously variable transmission 6 for driving a differential gear unit 1, a rotational direction switching means 7 for switching the input rotation of the fixed rotational power system F is provided, and connection is performed so that the continuously variable transmission 6 is operated when the power steering lever 8 is tilted over the predetermined value. The power of three systems, i.e., forward and reverse rotational vehicle speed follow-up power systems S1 and S2 and the fixed rotational power system F is selectively input via a uni-directional rotational clutch 9, and an output rotation switching means 10 is provided on the continuously variable transmission 6.