An apparatus and a method for controlling an automatic transmission that executes the learning of a shift point and provides an optimal upshift even when a vehicle is driven under conditions where resistance to driving varies greatly, such as when going up or down a hill or when towing. A reference engine acceleration is calculated and used to estimate a maximum engine rotational speed based on the relationship between the reference engine rotational acceleration and the engine rotational acceleration speed at an shift point. The shift point is corrected based on the deviation between the estimated engine rotational speed and a target maximum engine rotational speed at the shift point.