A reception data expander includes: an adaptive differential pulse code modulation (ADPCM) decoder activated when error detection information attains a reception data error nondetected state for expanding an input ADPCM code into a PCM (pulse code modulation) code, and inhibited of its decoding process operation when the error detection information indicates an error detected state; a memory circuit set to a write state when the error detection information attains an error nondetected state for sequentially storing generated ADPCM code, and outputting a stored PCM code when the error detection information is rendered to an error detected state; and a reconstructed output switch for selecting and providing to the next PCM decoder a PCM code when the error detection information attains an error nondetected state, and a PCM code read out from the memory circuit when the error detection information attains an error detected state. Noise generation arising from discontinuity of an ADPCM code at the time of reception data generation can be suppressed effectively without increasing the device complexity and power consumption.