When shifting an automatic transmission (3) into a higher gear, it is determined that an inertia phase has started when an input rotation speed of the automatic transmission (3) has started to decrease. Here, if throttle opening amount reduction control is being performed to reduce the output torque of the engine (2) when it is determined that the inertia phase has started, it is highly likely that determination is erroneous because that control causes the input rotation speed of the automatic transmission (3) (i.e., the engine speed) to decrease. When it is highly likely that the determination that the inertia phase has started is erroneous in this way, learning of a hydraulic pressure command value (Pt) is prohibited. As a result, erroneous learning of the hydraulic pressure command value (Pt) can be prevented.