A shift controller for an automatic transmission capable of automatically shifting up in a manual mode is provided. In the shift controller, a hysteresis between an automatic upshift line and a downshift permission line is set to be smaller as the accelerator opening degree decreases. As a result, when the accelerator opening degree is larger and therefore hunting is more likely to occur, it is possible to avoid an excessively small time interval between a downshift and an upshift. On the other hand, when the accelerator opening degree is smaller and therefore hunting is less likely to occur, a manual downshift permission region can be expanded to a higher rotational speed region, whereby a driver's manual downshift request can be satisfied in a higher vehicle speed region.