A control apparatus for an automatic transmission includes a vehicle speed detector and a controller. The vehicle speed detector is configured to detect a vehicle speed. The controller is configured to set one of a plurality of gear change stages according to a running condition of a vehicle and configured to select one of a plurality of engagement combination states of a plurality of engagement mechanisms to achieve, according to the vehicle speed detected by the vehicle speed detector, at least one gear change stage out of the plurality of gear change stages in a case in which the controller sets the at least one gear change stage. The at least one gear change stage has the plurality of engagement combination states to achieve the at least one gear change stage.