Voice decoding means 9 includes: voice decoding operation means 10 for performing a decoding operation on encoded voice data of a voice frame from the channel decoding means 6, thereby outputting an analog voice signal and voice power information of the voice frame; voice power operation means 14 for accumulating and averaging the voice power information, and outputting comparative power information; comparing means 16 for comparing voice power information of a received voice frame with the comparative power information, and for, when the difference is not smaller than a threshold, outputting a voice output control signal; and voice output control means 12 for controlling a volume of a voice frame having voice power information in which an abnormality is detected based on the voice output control signal. The voice decoding means 9 detects an erroneous voice frame on the basis of a difference between voice power information. The volume is controlled, so that the generation of an abnormal tone is prevented from occurring.
