A control apparatus and a control method for an automatic transmission installed in a vehicle, which detect an inclination of a road on which the vehicle is running; calculate actual torque of an engine installed in the vehicle; store reference torque of the engine; correct an inclination threshold value based on the actual torque and the reference torque and make a determination on whether ascending slope control or descending slope control needs to be performed in the vehicle based on the detected inclination of the road and the corrected inclination threshold value; and control the automatic transmission to perform the ascending slope control or the descending slope control based on the result of the determination. Thus, the control apparatus and the control method make an accurate determination on an ascending slope in a highland area, and accurately perform the ascending slope control or the descending slope control.