To improve the transmission efficiency without incurring a transmission delay increase.

Based on an identification result of a signal identification section that identifies whether an input signal is a voice signal or FAX signal, a voice signal subjected to short cell processing of the voice signal is stored in a queue buffer 21, while a FAX signal subjected to short cell processing of the FAX signal is stored in a queue buffer 22. The maximum permissible storage time of the queue buffer 22 is selected longer than that of the queue buffer 21.