An image decoding method for decoding a video signal comprising a plurality of images classified into layers, each of the plurality of images belonging to a corresponding one of the layers, the layers including a first layer and a second layer, wherein (i) when an image belonging to the first layer is decoded, the image belonging to the first layer is (i) able to refer to another image belonging to the first layer and (ii) is not able to refer to an image belonging to the second layer; and (ii) when an image belonging to the second layer is decoded, the image belonging to the second layer is able to (i) refer to an image belonging to the first layer and (ii) another image belonging to the second layer; the method further comprising decoding (i) a first image belonging to the first layer by referring to another image belonging to the first layer and (ii) a second image belonging to one of the first layer and the second layer by inter prediction, wherein the second image precedes the first image in decoding order; and decoding a third image belonging to the second layer by inter prediction, wherein the third image follows the first image in the decoding order; characterized in that in a case that the first image is a specified image to prohibit the third image from referring to the second image, the third image is decoded without referring to the second image preceding the first image in the decoding order; and in a case that the first image is not the specified image to prohibit the third image from referring to the second image, the third image is able to be decoded by referring to the second image preceding the first image in the decoding order. (i) when an image belonging to the first layer is decoded, the image belonging to the first layer is (i) able to refer to another image belonging to the first layer and (ii) is not able to refer to an image belonging to the second layer; and (ii) when an image belonging to the second layer is decoded, the image belonging to the second layer is able to (i) refer to an image belonging to the first layer and (ii) another image belonging to the second layer; the method further comprising decoding (i) a first image belonging to the first layer by referring to another image belonging to the first layer and (ii) a second image belonging to one of the first layer and the second layer by inter prediction, wherein the second image precedes the first image in decoding order; and decoding a third image belonging to the second layer by inter prediction, wherein the third image follows the first image in the decoding order; characterized in that in a case that the first image is a specified image to prohibit the third image from referring to the second image, the third image is decoded without referring to the second image preceding the first image in the decoding order; and in a case that the first image is not the specified image to prohibit the third image from referring to the second image, the third image is able to be decoded by referring to the second image preceding the first image in the decoding order. the method further comprising decoding (i) a first image belonging to the first layer by referring to another image belonging to the first layer and (ii) a second image belonging to one of the first layer and the second layer by inter prediction, wherein the second image precedes the first image in decoding order; and decoding a third image belonging to the second layer by inter prediction, wherein the third image follows the first image in the decoding order; characterized in that in a case that the first image is a specified image to prohibit the third image from referring to the second image, the third image is decoded without referring to the second image preceding the first image in the decoding order; and in a case that the first image is not the specified image to prohibit the third image from referring to the second image, the third image is able to be decoded by referring to the second image preceding the first image in the decoding order.