An automatic filtering method, comprising the steps of: (i) analyzing an input signal so as to obtain a frequency spectrum of the input signal; and (ii) selecting, on a basis of the frequency spectrum of the input signal, at least one filter from among a plurality of preset filters and filtering the input signal, the step (ii) including: determining, on the basis of the frequency spectrum of the input signal, a signal type included in the input signal; selecting, on a basis of the signal type included in the input signal, a corresponding filter corresponding to the signal type; filtering the input signal with use of a first parameter of the corresponding filter and setting a second parameter for the corresponding filter on a basis of a result of the filtering; and filtering the input signal with use of the second parameter set for the corresponding filter, the setting of the second parameter for the corresponding filter on the basis of the result of the filtering including: determining, on the basis of the result of the filtering, whether the type of signal which type corresponds to the corresponding filter has been filtered out; in a case where the determining shows that the type of signal which type corresponds to the corresponding filter has been filtered out, setting the first parameter of the corresponding filter as the second parameter; and in a case where the determining shows that the type of signal which type corresponds to the corresponding filter has not been filtered out, repeating a process of adjusting the first parameter of the corresponding filter and simulating a filtering result with use of the adjusted first parameter until the type of signal which type corresponds to the corresponding filter is filtered out and setting the adjusted first parameter as the second parameter. (i) analyzing an input signal so as to obtain a frequency spectrum of the input signal; and (ii) selecting, on a basis of the frequency spectrum of the input signal, at least one filter from among a plurality of preset filters and filtering the input signal, determining, on the basis of the frequency spectrum of the input signal, a signal type included in the input signal; selecting, on a basis of the signal type included in the input signal, a corresponding filter corresponding to the signal type; filtering the input signal with use of a first parameter of the corresponding filter and setting a second parameter for the corresponding filter on a basis of a result of the filtering; and filtering the input signal with use of the second parameter set for the corresponding filter, determining, on the basis of the result of the filtering, whether the type of signal which type corresponds to the corresponding filter has been filtered out; in a case where the determining shows that the type of signal which type corresponds to the corresponding filter has been filtered out, setting the first parameter of the corresponding filter as the second parameter; and in a case where the determining shows that the type of signal which type corresponds to the corresponding filter has not been filtered out, repeating a process of adjusting the first parameter of the corresponding filter and simulating a filtering result with use of the adjusted first parameter until the type of signal which type corresponds to the corresponding filter is filtered out and setting the adjusted first parameter as the second parameter.