Personal authentication apparatus, personal authentication method, and recording medium

A personal authentication apparatus includes a measuring circuit that measures a user electrocardiographic waveform using electrodes, a peak detector that detects peaks of first and second R waves and at least one of peaks of P and Q waves, and an acquirer. The acquirer expands/contracts a time interval between the peaks of the first and second R waves to a first time period and further (i) expands/contracts a time interval between the peaks of the first R wave and P wave to a second time period, (ii) expands/contracts a time interval between the peaks of the first R wave and Q wave to a third time period, or (iii) expands/contracts the time interval between the peaks of the first R wave and P wave to the second time period and expands/contracts the time interval between the peaks of the first R wave and Q wave to the third time period.