To provide a control device for an automatic transmission, rapidly converging to highly accurate predicted vehicle speed when returning from an abnormal state to a normal state while preventing occurrence of rapid gear shift even if a signal determining a traveling condition is abnormal.

When an input state determination means determines that a vehicle speed sensor is abnormal, a vehicle speed estimation means continues calculation by using a first alternative value in response to the traveling condition when determining abnormality, and also a target gear shift ratio is calculated using a second alternative value. When the vehicle speed sensor is changed from in an abnormal state to a normal state, the first alternative value is returned to the actual vehicle speed and the predicted vehicle speed is calculated. When a predetermined condition is satisfied, the second alternative value is returned to the predicted vehicle speed, thereby allowing calculation of the target gear shift ratio by the predicted vehicle speed.