PURPOSE: To constantly secure the favorable shift feelind by shifting the shift line based on the vehicle speed and the engine load based on the prescribed coefficient, and switching a plurality of shift maps based on this coefficient and the movement according to the change of the road traffic condition.

CONSTITUTION: The output of the engine 1 is transmitted to driving wheels through an automatic transmission 2 consisting of a torque converter 4, a speed change gear drive 3, a hydraulic circuit 5, etc. A controller 40 controls the speed of the automatic transmission 2 based on the detected signals from at least a turbine speed sensor 21, a transfer drive gear speed sensor 22, and a throttle valve opening sensor 23. The driving condition of a driver and the gradient of the road are respectively judged, the prescribed coefficient is set based on this judgement value, and the shift line of the shift map based on the vehicle speed and the engine load is moved according to this coefficient. A plurality of shift maps based on the coefficient and the movement are switched according to the change of the road traffic condition.