There is provided a control device for a transmission for shifting a driving force of an engine. The transmission includes at least two input shafts configured to be driven by the driving force of the engine, intermediate shafts provided correspondingly to the at least two input shafts and configured such that driving forces of the input shafts are respectively transmitted thereto, and a clutch provided between the input shafts and the intermediate shafts and configured to transmit the driving forces from the input shafts to the intermediate shafts. A non-use shaft detection section is configured to detect a non-use state of the intermediate shafts based on a transmission state of the clutch.