Provided is a switchable Correlated Color Temperature (CCT) illuminating device. The device may include a CCT switching unit, forming electrical connection with a drive power source, and a bulb shell, at least one filament being arranged inside the bulb shell, the filament including a substrate, and a first light-emitting unit group and a second light-emitting unit group arranged on the substrate and forming electrical connection with the CCT switching unit. Each of the first light-emitting unit group and the second light-emitting unit group comprises one or more light-emitting unit, the first light-emitting unit group and the second light-emitting unit group are connected in parallel and conducting directions thereof are opposite, and when one of the first light-emitting unit group and the second light-emitting unit group is in a positive ON status, the other is in a negative OFF status. When the CCT switching unit is in a first operating mode, the first light-emitting unit group is in the positive ON status, and the CCT switchable illuminating device emits light with a first CCT. When the CCT switching unit is in a second operating mode, the second light-emitting unit group is in electrical conduction, and the CCT switchable illuminating device emits light with a second CCT. Therefore, the problem that the illuminating device in the prior art has a single CCT is solved.