A control device for an automatic transmission includes: a failure diagnosis section for diagnosing whether or not a failure has occurred in a shift control system of the automatic transmission; a fail-safe control section for fixing the automatic transmission into a predetermined gear position in response to confirmation of the failure of the shift control system of the automatic transmission; and an oil temperature rise regulation torque reduction control section for outputting a torque reduction request to suppress torque of a vehicle driving source, based on temperature of transmission operating oil of the automatic transmission, and outputting the torque reduction request in response to satisfaction of an oil temperature condition that is set lower in oil temperature when the automatic transmission is fixed in a first gear position by the fail-safe control section than when the automatic transmission is not fixed in the first gear position.