PURPOSE: To accomplish smooth starting without operating a sub-speed change gear switched to a speed increasing position to a direct coupling position by detecting the stop of a vehicle and automatically shifting the sub-speed change gear to the direct coupling position.

CONSTITUTION: A car velocity zero detecting means 22 for detecting the stop of a vehicle includes a car velocity sensor and a circuit for detecting the car velocity zero from an output of the car velocity sensor. The output of the car velocity zero detecting means 22 is given to a driving circuit 20 through OR gate 19, and on receiving the detection output, the driving circuit 20 is adapted to drive a shift actuator 15 similarly to the case of receiving a switch output of a low-speed shift switch 16 to switch a main drive shaft 3 to a direct coupling position to be direct-coupled to a speed change gear 6.