A control device of a diesel engine is provided. The diesel engine includes an injector for injecting fuel into a cylinder, and a turbocharger for compressing intake air by using exhaust energy. The control device includes a calculating module for setting a basic injection timing determined according to an operating state of the engine, as a timing of injecting the fuel from the injector, and an injection control module for injecting the fuel from the injector at the set basic injection timing at least while the engine is in a steady operation.