An alcohol-drinking detecting system which is provided with an alcohol-drinking analyzing and estimating section configured to analyze a pulse wave as a biological signal obtained from an upper body of a person by a biological signal measuring device to estimate presence/absence of alcohol in the body, wherein the alcohol-drinking analyzing and estimating section comprises: a frequency dynamic information processing means configured to obtain, from a time-series waveform of the biological signal, a time-series fluctuation regarding the dominant frequency of the time series-waveform; wherein the frequency dynamic information processing means comprises a frequency computing means configured to obtain a time-series waveform of the dominant frequency in the time-series waveform of the biological signal, and a frequency slope time-series analyzing and computing means configured to perform a moving calculation for obtaining, in the time-series waveform of the dominant frequency of the biological signal obtained by the frequency computing means, a slope of the frequency for each of predetermined time windows set in a predetermined overlapping time to output a time-series change of the slope of the frequency obtained for each time window as a frequency slope time-series waveform; and an alcohol-drinking state determining means configured to determine an alcohol-drinking state when a tendency of the time-series fluctuation regarding the frequency obtained from the frequency dynamic information processing means is separated from a tendency of the time-series fluctuation regarding the frequency at a non-drinking time according to whether or not, regarding a difference of an integral value of a positive slope and a difference of an integral value of a negative slope obtained by dividing the frequency slope time-series waveform into the positive slope and the negative slope to integrate the respective positive and negative slopes and comparing the integral values of the positive slope and the negative slope with those in a normal state before alcohol drinking, the difference of the integral value of the positive slope decreases to a predetermined difference or more and the difference of the integral value of the negative slope increases to a predetermined difference or more. a frequency dynamic information processing means configured to obtain, from a time-series waveform of the biological signal, a time-series fluctuation regarding the dominant frequency of the time series-waveform; wherein the frequency dynamic information processing means comprises a frequency computing means configured to obtain a time-series waveform of the dominant frequency in the time-series waveform of the biological signal, and a frequency slope time-series analyzing and computing means configured to perform a moving calculation for obtaining, in the time-series waveform of the dominant frequency of the biological signal obtained by the frequency computing means, a slope of the frequency for each of predetermined time windows set in a predetermined overlapping time to output a time-series change of the slope of the frequency obtained for each time window as a frequency slope time-series waveform; and an alcohol-drinking state determining means configured to determine an alcohol-drinking state when a tendency of the time-series fluctuation regarding the frequency obtained from the frequency dynamic information processing means is separated from a tendency of the time-series fluctuation regarding the frequency at a non-drinking time according to whether or not, regarding a difference of an integral value of a positive slope and a difference of an integral value of a negative slope obtained by dividing the frequency slope time-series waveform into the positive slope and the negative slope to integrate the respective positive and negative slopes and comparing the integral values of the positive slope and the negative slope with those in a normal state before alcohol drinking, the difference of the integral value of the positive slope decreases to a predetermined difference or more and the difference of the integral value of the negative slope increases to a predetermined difference or more.