A transmission control apparatus for an automatic transmission to change a shift position automatically includes a cornering-state judging device, a modified shift-up table generator, and a gear-shift controller. The cornering-state judging device is configured to judge whether a vehicle has transitioned to a cornering state from a normal running state. The modified shift-up table generator is configured to generate a modified shift-up table when the vehicle is judged to have transitioned to the cornering state. The modified shift-up table makes a shift-up more difficult to occur than a reference shift-up table does. The gear-shift controller is configured to perform gear-shift control by using the reference shift-up table during the normal running state. The gear-shift controller is configured to suppress a gear shift by using the modified shift-up table instead of the reference shift-up table when the vehicle is judged to have transitioned to the cornering state.