A TWA measuring apparatus includes: a T-wave feature quantity measuring section a classifying section classifying T-wave feature quantities into groups of odd and even electrocardiogram waveforms a reliability index calculating section calculating: first and second representative values and first and second dispersion values of the T-wave feature quantities in the odd and even group a difference between the first and second representative values, to obtain a TWA feature quantity and an adjustment value between the first representative value and the first dispersion value, and an adjustment value between the second representative value and the second dispersion value, to obtain a reliability index and a reliability recognizing section recognizing: when the reliability index exceeds a threshold, that reliability of the TWA feature quantity is high and when the reliability index does not exceed the threshold, that the reliability is low.
