A speech coding apparatus that includes at least two coding layers, including a lower coding layer and a higher coding layer, wherein: the lower layer (205, 206, 207) is adapted to receive as input a lower layer input signal of a frequency domain; select a first quantization target band of the lower layer input signal from a plurality of sub-bands into which the frequency domain is divided; encode the lower layer input signal of the first quantization target band to generate first coded information including first band information, indicating the first quantization target band, and first shape coded information and first gain coded information together presenting an encoded spectrum of the lower layer input signal in the first quantization target band; generate a first decoded signal by decoding the encoded spectrum of the lower layer input signal from the first coded information, the decoding using demultiplexing the first coded information into the first band information, the first shape coded information and the first gain coded information; and generate a higher layer input signal as a difference between the lower layer input signal and the first decoded signal; and the higher layer is adapted to receive as input the higher layer input signal and the first decoded signal thereto; select a second quantization target band of the higher layer input signal from the plurality of sub-bands, by utilizing a perception masking effect of the first decoded signal; encode the higher layer input signal of the second quantization target band; and generate second coded information including second band information indicating the second quantization target band. the lower layer (205, 206, 207) is adapted to receive as input a lower layer input signal of a frequency domain; select a first quantization target band of the lower layer input signal from a plurality of sub-bands into which the frequency domain is divided; encode the lower layer input signal of the first quantization target band to generate first coded information including first band information, indicating the first quantization target band, and first shape coded information and first gain coded information together presenting an encoded spectrum of the lower layer input signal in the first quantization target band; generate a first decoded signal by decoding the encoded spectrum of the lower layer input signal from the first coded information, the decoding using demultiplexing the first coded information into the first band information, the first shape coded information and the first gain coded information; and generate a higher layer input signal as a difference between the lower layer input signal and the first decoded signal; and the higher layer is adapted to receive as input the higher layer input signal and the first decoded signal thereto; select a second quantization target band of the higher layer input signal from the plurality of sub-bands, by utilizing a perception masking effect of the first decoded signal; encode the higher layer input signal of the second quantization target band; and generate second coded information including second band information indicating the second quantization target band.