An electrocardiogram signal derived from electrocardiogram measuring means 1 and a pulse signal derived from pulse-wave measuring means 2 are applied to a CPU 30. The CPU 30 processes the cardiogram signal to detect a QRS wave signal, and processes the pulse signal to detect the amplitude of the pulse signal. The CPU 30 judges whether or not the QRS wave is caused by a ventricular premature contraction. If two QRS waves, not caused by ventricular premature contraction, occurs successively, and the CPU 30 judges if A0.times.k>A1. The CPU 30 judges that a supraventricular extrasystole is occurred. Here, A0 is an amplitude of the first QSR wave; A1 is an amplitude of the second QSR wave; and k is a preset value, 0