an image decoding device and an image decoding method are disclosed . the decoding device includes : a variable length decoder to variable - length - decode an inputted encoded bit stream to obtain a parameter for prediction signal generation , a compressed difference image , and filters ; and a filtering processor to carry out a filtering process on a decoded image acquired by adding a prediction image and a difference image , wherein the prediction image is generated by using the parameter for prediction signal generation , and the difference image is acquired by decoding the compressed difference image , wherein the variable length decoder variable - length - decodes class identification information for a block in the decoded image , and wherein the filtering processor refers to the class identification information for the block to determine a class for the block , and carries out a filtering process on the block based on the determined class and the filters .