A scaling device for receiving and scaling a digital image signal includes a scaling module and a data quantity control logic. The scaling module scales the digital image signal and then outputs a scaled output signal according to a scaling ratio. The data quantity control logic controls output quantity of the scaled output signal according to a scaling ratio. Thus, when the data quantity outputted from the scaling module is controlled within the data quantity that may be processed by the post stage of the scaling module per unit time, the data quantities that may be processed per unit time in the post stage processing devices of the scaling module approximate a constant value such that the post stage processing speed of the scaling module may be increased.