A control device and method of a spark-ignition gasoline engine is provided. An engine operates in a compression ignition model in a low load area and in a spark ignition model in a high load area. In the spark ignition model, within a retard period from a late stage of a compression stroke to an early stage of an expansion stroke, an external EGR is executed for control. In a switching area with comparatively lower load in an execution area in the spark ignition model, an EGR rate controlled by the external EGR is set higher than a load of the switching area and filling quantity control for making an intake filling quantity lower than an intake filling quantity of the compression ignition model. Accordingly, combustion stability in the spark ignition model can be raised and the load area for reducing intake filling quantity can be reduced as much as possible.