To solve a problem of reduction in encoding efficiency due to redundancy caused by independently encoding a luminance intra prediction mode and a color difference intra prediction mode.

A luminance intra prediction mode encoding section 601 encodes an in-screen prediction mode of a luminance component in a block to be encoded. A color difference intra prediction mode encoding section 603 refers to the in-screen prediction mode of the luminance component in the block to be encoded and encodes color difference prediction mode determining information specifying an in-screen prediction mode of a color difference component in a block to be encoded. The color difference intra prediction mode encoding section 603 encodes the color difference prediction mode determining information showing vertical/horizontal mode having, as an in-screen prediction mode of a color difference component in the block to be encoded, a mode forming a small angle or a large angle with the in-screen prediction mode of the luminance component in the block to be encoded from the vertical/horizontal mode which is the in-screen prediction mode of the color difference component.