A voice communication system is equipped with a voice encoder which classifies respective bits of a voice information bit string in accordance with the degree of importance which is the magnitude of auditory influence when there is an error therein, classifies a group of bits which are high in degree of importance into a core layer and classifies a group of bits which are not high into an extension layer and a voice decoder which decodes a voice by using the bit strings in both of the core layer and the extension layer on the basis of frequency that the error is detected by error detection processing and when the frequency is low and decodes the voice using all bits or only some bets in the core layer when the frequency is high.