An image processing device and an image processing method are provided. The image processing device includes multiple image input units, an expansion module, a controller, and an image processing module. The multiple image input units are configured to receive multiple image signals and convert the multiple image signals into multiple converted image signals. The multiple converted image signals have a first image format. The expansion module is detachably coupled to the multiple image input units and is configured to output selected image signals according to a first selection signal. The controller is configured to provide the first selection signal. The image processing module is configured to receive the selected image signals to integrate into a picture in picture.