Disclosed is a biological information processing apparatus and a signal processing method, wherein a biological signal comprising a first signal component having periodicity is generated, and a given frequency distribution is generated based on a second-order difference signal obtained by subjecting the biological signal to a second-order differencing operation, whereafter, with respect to the generated frequency distribution, an effective greatest frequency zone which is a zone having a greatest frequency of an interval-time is determined based on a given criterion, and a period of the first signal component is calculated based on an average time interval in the effective greatest frequency zone.
