Abstract: An apparatus for controlling an automatic transmission of an automobile and a method therefor utilize a route guidance system. The apparatus includes a memory which stores road information, a detector for detecting a specific position which is located on a planned driving route from the road information stored in the memory; a position detector for detecting the present position of the automobile; a speed detector for detecting the speed V of the automobile; a sensor for detecting an opening degree .theta. of a throttle of the automobile; a computer for computing a distance "d" between the detected automobile position and the detected specific position; a driving operation detector for detecting an operation by the driver of the automobile; a first gear ratio selecting device for selecting a first gear ratio for the automatic transmission based on the detected speed V and the detected throttle opening degree .theta.