An audio decoding method by an audio decoding device for decoding an audio code and outputting an audio signal, comprising: an audio code buffer step of detecting packet loss, with the audio decoding device, based on a received state of an audio packet; an audio parameter decoding step of decoding an audio code, with the audio decoding device, when an audio packet is correctly received; a side information decoding step of decoding a side information code, with the audio decoding device, when the audio packet is correctly received; a side information accumulation step of storing, with the audio decoding device, side information obtained by decoding the side information code in the side information decoding step in a buffer, the side information being related to a pitch lag and/or an adaptive codebook gain in a look-ahead signal; an audio parameter missing processing step of outputting, with the audio decoding device, an audio parameter when audio packet loss is detected; an audio parameter accumulation step of storing the audio parameter in a buffer when an audio packet is correctly received; and an audio synthesis step of synthesizing, with the audio decoding device, a decoded audio from the audio parameter, wherein the audio parameter missing processing step comprises calculating, with the audio decoding device when audio packet loss is detected, a predicted value of the audio parameter using the audio parameter stored when the audio packet is correctly received and the side information stored in the side information accumulation step, and if a reliability of the audio parameter is low, the audio decoding device adopting the side information stored in the side information accumulation step as the audio parameter. an audio code buffer step of detecting packet loss, with the audio decoding device, based on a received state of an audio packet; an audio parameter decoding step of decoding an audio code, with the audio decoding device, when an audio packet is correctly received; a side information decoding step of decoding a side information code, with the audio decoding device, when the audio packet is correctly received; a side information accumulation step of storing, with the audio decoding device, side information obtained by decoding the side information code in the side information decoding step in a buffer, the side information being related to a pitch lag and/or an adaptive codebook gain in a look-ahead signal; an audio parameter missing processing step of outputting, with the audio decoding device, an audio parameter when audio packet loss is detected; an audio parameter accumulation step of storing the audio parameter in a buffer when an audio packet is correctly received; and an audio synthesis step of synthesizing, with the audio decoding device, a decoded audio from the audio parameter, wherein the audio parameter missing processing step comprises calculating, with the audio decoding device when audio packet loss is detected, a predicted value of the audio parameter using the audio parameter stored when the audio packet is correctly received and the side information stored in the side information accumulation step, and if a reliability of the audio parameter is low, the audio decoding device adopting the side information stored in the side information accumulation step as the audio parameter.