In a planetary gear type stepped automatic transmission, a gear shift control to shift a gear shift stage between a first gear shift stage and a second gear shift stage is performed by a first shift control section by referring to a first gear shift control data used when the gear shift stage is switched between the first gear shift stage and the second gear shift stage, an abnormality state due to a failure of at least one of a first frictional engaging element and a second frictional engaging element is detected, and an abnormality state gear shift control is performed to shift the gear shift stage between a third gear shift stage (for example, first speed) and a fourth gear shift stage (for example, 2.5 speed) by the first shift control section, while forcefully releasing the first frictional engaging element, when detecting the abnormality state.