A signal processing apparatus (100, 500) comprising: a separation section that is adapted to separate a mixed sound signal, in which a plurality of excitations are mixed, into the respective excitations; a speech detection section that is adapted to perform speech detection on the plurality of separated excitation signals, judge whether or not the plurality of excitation signals are speech and generate speech section information indicating speech/non-speech information for each excitation signal; an extraction section (150, 510) that is adapted to extract identification parameters indicating feature values of a daily conversation based on the plurality of excitation signals or the speech section information; and a conversation establishment degree calculation section (160, 520) that is adapted to calculate a degree of establishment of a conversation based on the extracted identification parameters, the degree of establishment of a conversation indicating a degree for identifying an utterance of a conversation partner and an utterance of a non-conversation partner, characterized in that: the extraction section (150, 510) includes an utterance overlap duration extraction section (151, 511) that is adapted to calculate, using the speech section information, an average utterance overlap duration or a ratio of a sum of the utterance overlap durations which are shorter than a threshold and a sum of the utterance overlap durations as a first of the identification parameters, and a silence duration extraction section (152, 512) that is adapted to calculate, using the speech section information, an average silence duration or a ratio of sum of the silence durations which are shorter than the threshold and a sum of the silence durations as a second of the identification parameters; and the conversation establishment degree calculation section (160, 520) is adapted to calculate the degree of establishment of a conversation by using the first identification parameter, calculated from the utterance overlap duration, and the second identification parameter. calculated from the silence duration. a separation section that is adapted to separate a mixed sound signal, in which a plurality of excitations are mixed, into the respective excitations; a speech detection section that is adapted to perform speech detection on the plurality of separated excitation signals, judge whether or not the plurality of excitation signals are speech and generate speech section information indicating speech/non-speech information for each excitation signal; an extraction section (150, 510) that is adapted to extract identification parameters indicating feature values of a daily conversation based on the plurality of excitation signals or the speech section information; and a conversation establishment degree calculation section (160, 520) that is adapted to calculate a degree of establishment of a conversation based on the extracted identification parameters, the degree of establishment of a conversation indicating a degree for identifying an utterance of a conversation partner and an utterance of a non-conversation partner, the extraction section (150, 510) includes an utterance overlap duration extraction section (151, 511) that is adapted to calculate, using the speech section information, an average utterance overlap duration or a ratio of a sum of the utterance overlap durations which are shorter than a threshold and a sum of the utterance overlap durations as a first of the identification parameters, and a silence duration extraction section (152, 512) that is adapted to calculate, using the speech section information, an average silence duration or a ratio of sum of the silence durations which are shorter than the threshold and a sum of the silence durations as a second of the identification parameters; and the conversation establishment degree calculation section (160, 520) is adapted to calculate the degree of establishment of a conversation by using the first identification parameter, calculated from the utterance overlap duration, and the second identification parameter. calculated from the silence duration.