An image processing device comprising: a decoding section that generates a decoded image by performing a decoding process of a bitstream; and a filtering section that applies, as a second color-difference filter having a higher filter strength than a first color-difference filter, a reduced second luminance filter or a reduced first luminance filter to a pixel of a color-difference component located around a block boundary in the decoded image having undergone the decoding process by the decoding section, wherein the reduced second luminance filter has a reduced filter characteristic with respect to a second luminance filter having a higher filter strength than a first luminance filter, and the reduced first luminance filter has a reduced filter characteristic with respect to the first luminance filter, wherein the reduced second luminance filter is a reduced second luminance vertical filter that executes the reduced second luminance filter in a vertical direction, and the second color-difference filter is a second color-difference vertical filter that executes the second color-difference filter in the vertical direction, a control section that controls the filtering section such that the reduced second luminance vertical filter is applied, as the second color-difference vertical filter, to a block boundary of a CTU; wherein the control section controls the filtering section such that a second luminance vertical filter that executes the second luminance filter in the vertical direction is applied, as the second color-difference vertical filter, to an internal block boundary of a block divided from the coding tree block. a decoding section that generates a decoded image by performing a decoding process of a bitstream; and a filtering section that applies, as a second color-difference filter having a higher filter strength than a first color-difference filter, a reduced second luminance filter or a reduced first luminance filter to a pixel of a color-difference component located around a block boundary in the decoded image having undergone the decoding process by the decoding section, wherein the reduced second luminance filter has a reduced filter characteristic with respect to a second luminance filter having a higher filter strength than a first luminance filter, and the reduced first luminance filter has a reduced filter characteristic with respect to the first luminance filter, wherein the reduced second luminance filter is a reduced second luminance vertical filter that executes the reduced second luminance filter in a vertical direction, and the second color-difference filter is a second color-difference vertical filter that executes the second color-difference filter in the vertical direction, a control section that controls the filtering section such that the reduced second luminance vertical filter is applied, as the second color-difference vertical filter, to a block boundary of a CTU; wherein the control section controls the filtering section such that a second luminance vertical filter that executes the second luminance filter in the vertical direction is applied, as the second color-difference vertical filter, to an internal block boundary of a block divided from the coding tree block. <EOS>