An audio signal coding apparatus comprising: a time-frequency transformer that generates a spectrum comprising performing a transform on an input audio signal into a frequency domain, divides the spectrum into a plurality of sub-bands, which are predetermined frequency bands, and outputs sub-band spectral samples; a sub-band energy quantizer that obtains, for each of the plurality of sub-bands, a quantized sub-band energy; a tonality calculator that analyzes a tonality of the sub-band spectral samples and output an analysis result; a bit allocator that selects a second sub-band on which quantization is performed by a second quantizer from among the plurality of sub-bands on the basis of the analysis result for the tonality and the quantized sub-band energy, and determines a first number of bits to be allocated to a first sub-band, among the plurality of sub-bands, on which quantization is performed by a first quantizer; and a multiplexer that multiplexes information output from the first quantizer and from the second quantizer, the quantized sub-band energy, and the analysis result of the tonality, and outputs the multiplexed information, wherein the first quantizer codes a sub-band spectral sample among the sub-band spectral samples that is included in the first sub-band by a first coding method using the first number of bits, and the second quantizer codes a sub-band spectral sample among the sub-band spectral samples that is included in the second sub-band by a second coding method to obtain the coded information output from the second quantizer, wherein the second coding method is configured for calculating lag information for the second subband. a time-frequency transformer that generates a spectrum comprising performing a transform on an input audio signal into a frequency domain, divides the spectrum into a plurality of sub-bands, which are predetermined frequency bands, and outputs sub-band spectral samples; a sub-band energy quantizer that obtains, for each of the plurality of sub-bands, a quantized sub-band energy; a tonality calculator that analyzes a tonality of the sub-band spectral samples and output an analysis result; a bit allocator that selects a second sub-band on which quantization is performed by a second quantizer from among the plurality of sub-bands on the basis of the analysis result for the tonality and the quantized sub-band energy, and determines a first number of bits to be allocated to a first sub-band, among the plurality of sub-bands, on which quantization is performed by a first quantizer; and a multiplexer that multiplexes information output from the first quantizer and from the second quantizer, the quantized sub-band energy, and the analysis result of the tonality, and outputs the multiplexed information, wherein the first quantizer codes a sub-band spectral sample among the sub-band spectral samples that is included in the first sub-band by a first coding method using the first number of bits, and the second quantizer codes a sub-band spectral sample among the sub-band spectral samples that is included in the second sub-band by a second coding method to obtain the coded information output from the second quantizer, wherein the second coding method is configured for calculating lag information for the second subband.