PURPOSE: To secure a feeling of proper acceleration as preventing a slip so properly by setting a period of closing control over a throttle valve at time of shift of a transmission down to a period of time engine speed is lowered up to the specified rate with the engine speed at a point of shift starting time.

CONSTITUTION: An output shaft of an internal combustion engine 10 is connected to a driving wheel 48 via an automatic transmission 28. In this case, when an accelerating slip is detected by a means A on the basis of each speed of the driving wheel 48 and a driven wheel 50, opening of a throttle valve 22 is set by a means B so as to eliminate the slip in conformity with the progress of acceleration. In addition, when a shift-up of the automatic transmission 28 is detected by a means C, the opening of the throttle valve 22 is fixed and set to the more closing side than the said setting opening by a means D. When engine speed further detected by a means 47 after shift-up detection is lowered, any setting by the means D of the throttle valve 22 is suspended and thereby it is controlled by a means E so as to be reset to the setting by the means B.