PURPOSE: To suppress and stop to carry out shift-down sensitively so as to improve driving performance of a vehicle by inhibiting down-shift control for a prescribed period when operating condition of an internal combustion engine is moved from operating condition of lean air-fuel ratio to operating condition of down-shift.

CONSTITUTION: An automatic transmission 2 is combined in an internal combustion engine 1 an electronic control fuel injection device is arranged in the internal combustion engine 1, which is arranged in order to generate mixture air of a prescribed air-fuel ratio by controlling a fuel injection valve by a control unit 3 for controlling the engine 1. The control unit 3 for controlling the engine 1 is connected to various kinds of sensors 4 to 8 for detecting engine operating condition respectively. The automatic transmission 2 is controlled by a control unit 9 for an A/T which is connected to the inhibitor switch 11 of an A/T select lever 10 and the like. In this case, when operating condition of the internal combustion engine 1 is moved from operating condition of lean air-fuel ratio to operating condition of down-shift, down-shift control is inhibited for a prescribed period.