Gear shift control apparatus and method for automatic transmission

In gear shift control apparatus and method for an automatic transmission, a first frictional engagement element is, in turn, released, a second frictional engagement element is, in turn, engaged to perform the gear shift to another gear stage, a command hydraulic pressure to the second frictional engagement element is temporarily reduced when a parameter indicating a degree of progress of the gear shift detected during the gear shift to the other gear stage has reached to a predetermined value representing an inertia phase finish immediate prior region at a time of an inertia phase developed during a replacement gear shift, an reduction quantity of the command hydraulic pressure is set whenever a predetermined time has elapsed on a basis of the parameter detected whenever the predetermined time has elapsed in the inertia phase finish immediate prior region to progressively reduce the command hydraulic pressure.