An audio signal processing device comprising: a-display device comprising: multiple input reception units to which respective analog audio signals, on which watermark information indicating corresponding identification information of respective audio devices is superimposed in an inaudible range of the respective analog audio signals, are input from the respective audio devices; an extraction unit that is adapted to extract the identification information from the respective analog audio signals input to the multiple input reception units; a display unit that is adapted to perform display depending on the identification information extracted by the extraction unit in correspondence with the input reception unit to which the analog audio signal, from which the identification information is extracted, is input; and a removal unit that is adapted to remove the watermark information superimposed on the respective analog audio signals; and a signal processing unit that is adapted to perform signal processing set in advance for the analog audio signal input to the input reception unit and output the processed analog audio signal and is adapted to mix the analog audio signals subjected to the signal processing with each other and to output the mixed analog audio signal. a-display device comprising: multiple input reception units to which respective analog audio signals, on which watermark information indicating corresponding identification information of respective audio devices is superimposed in an inaudible range of the respective analog audio signals, are input from the respective audio devices; an extraction unit that is adapted to extract the identification information from the respective analog audio signals input to the multiple input reception units; a display unit that is adapted to perform display depending on the identification information extracted by the extraction unit in correspondence with the input reception unit to which the analog audio signal, from which the identification information is extracted, is input; and a removal unit that is adapted to remove the watermark information superimposed on the respective analog audio signals; and multiple input reception units to which respective analog audio signals, on which watermark information indicating corresponding identification information of respective audio devices is superimposed in an inaudible range of the respective analog audio signals, are input from the respective audio devices; an extraction unit that is adapted to extract the identification information from the respective analog audio signals input to the multiple input reception units; a display unit that is adapted to perform display depending on the identification information extracted by the extraction unit in correspondence with the input reception unit to which the analog audio signal, from which the identification information is extracted, is input; and a removal unit that is adapted to remove the watermark information superimposed on the respective analog audio signals; and a signal processing unit that is adapted to perform signal processing set in advance for the analog audio signal input to the input reception unit and output the processed analog audio signal and is adapted to mix the analog audio signals subjected to the signal processing with each other and to output the mixed analog audio signal.