In a shift control device and a shift control method of an automatic transmission that establishes a plurality of gear steps of different speed change ratios by selectively engaging a plurality of friction engagement devices, one of a shift start time point and an inertia phase start time point is used as a reference time. In a power-off shift, the shift action is compulsorily ended when the elapsed time from the reference time exceeds a first time. In a power-on shift, the shift action is compulsorily ended when the elapsed time from the reference time exceeds a second time that is set shorter than the first time. If a switch from the power-off shift to the power-on shift occurs halfway through the power-off shift, the shift action is compulsorily ended when the elapsed time from the time point of the switch exceeds a predetermined time.