An image decoding method for decoding a coded stream generated by coding which includes orthogonal transform and quantization which includes a plurality of processing units (CU, PU, TU) and a header for the processing units, the coded stream being generated by coding a moving picture, at least one of the processing units being layered into one or more hierarchical layers each of which includes one or more sub-units whose sizes are smaller than a size of the processing unit, the image decoding method comprising the steps of: requesting an external system to send the coded stream: receiving the requested coded stream from the external system; parsing (S1; S101; S700; S900) depth information stored in the header, the depth information specifying a depth of a first hierarchical layer that a first sub-unit belongs to, the first sub-unit being a sub-unit in which a quantization parameter is stored; and decoding (S102; S712; S912) the processing unit by performing an inverse quantization on a second sub-unit that belongs to a second hierarchical layer using the quantization parameter, the second hierarchical layer being lower than the first hierarchical layer and the second sub-unit being a transform unit, which is a basic unit for specifying the transform and quantization process, and wherein the processing units include a coding unit that belongs to a highest hierarchical layer and a transform unit that belongs to a lower hierarchical layer which is lower than that of the coding unit. requesting an external system to send the coded stream: receiving the requested coded stream from the external system; parsing (S1; S101; S700; S900) depth information stored in the header, the depth information specifying a depth of a first hierarchical layer that a first sub-unit belongs to, the first sub-unit being a sub-unit in which a quantization parameter is stored; and decoding (S102; S712; S912) the processing unit by performing an inverse quantization on a second sub-unit that belongs to a second hierarchical layer using the quantization parameter, the second hierarchical layer being lower than the first hierarchical layer and the second sub-unit being a transform unit, which is a basic unit for specifying the transform and quantization process, and wherein the processing units include a coding unit that belongs to a highest hierarchical layer and a transform unit that belongs to a lower hierarchical layer which is lower than that of the coding unit. receiving the requested coded stream from the external system; parsing (S1; S101; S700; S900) depth information stored in the header, the depth information specifying a depth of a first hierarchical layer that a first sub-unit belongs to, the first sub-unit being a sub-unit in which a quantization parameter is stored; and decoding (S102; S712; S912) the processing unit by performing an inverse quantization on a second sub-unit that belongs to a second hierarchical layer using the quantization parameter, the second hierarchical layer being lower than the first hierarchical layer and the second sub-unit being a transform unit, which is a basic unit for specifying the transform and quantization process, and wherein the processing units include a coding unit that belongs to a highest hierarchical layer and a transform unit that belongs to a lower hierarchical layer which is lower than that of the coding unit.