Provided are an apparatus and method for selecting one of an image signal input from an image signal inputting device and an image signal obtained by changing the size of the image signal input from the image signal inputting device and displaying the selected image signal on a display device. The apparatus includes an image size converter for changing the size of a first image signal and outputting the result as a second image signal; and a selector for receiving the first and second image signals and selectively outputting one of the first and second image signals in response to a first control signal. With the apparatus and method, it is possible to selectively reproduce a high-definition image and a low-definition image.