In the case where a deblocking filter applied to a luminance component is referred to and applied to a chrominance component, by converting a pixel position of the chrominance component so as to have a pixel position of a luminance component which belongs to a same field as the chrominance component (F7a) and referring to the luminance component, the present invention makes it possible to generate a more natural image by filtering the luminance component and the chrominance component with the same strength when the image is displayed in an interlaced-scan form.