A heartbeat signal processor (20) includes a first and second electrodes (10a, 10b) to obtain a first and second heartbeat signals (50L, 50R) , a DC voltage calculating unit (21) and an AC amplitude calculating unit (22) to calculate first and second average DC voltage values of direct-current components and first and second average AC amplitude values of alternate-current components in the first and second heartbeat signals,a correlation coefficient calculating unit (23) to calculate a correlation coefficient between the alternate-current components in the first and second heartbeat signals, an amplification factor setting unit (24) to set an amplification factor on the basis of the first and second average DC voltage values, the first and second average AC amplitude values, and the correlation coefficient, and a signal generating unit (26) to generate a differential heartbeat signal by amplifying the first or second heartbeat signal on the basis of the amplification factor and calculating a difference (50D) between the first and second heartbeat signals.
