Provided is a signal demultiplexing system that can minimize losses in demultiplexing performance even if signals unsuited to demultiplexing are inputted. The provided signal demultiplexing device contains: an input signal analysis means for determining whether or not a plurality of input signals are suited to demultiplexing; a data memory means for storing data from frequency-domain input signals which result from transformation of the aforementioned input signals into frequency-domain signals; a selection control means for storing the frequency-domain input signals in the data memory means if the input signal analysis means has determined that the input signals are suited to the generation of a demultiplexing matrix for demultiplexing; and a demultiplexing matrix generation means for generating a demultiplexing matrix using frequency-domain input signals including the most recent and older frequency-domain input signals stored in the data memory means.