An electrocardiogram analyzer includes a first acquiring section that acquires a body surface electrocardiogram of a subject, a second acquiring section that acquires an intracardiac electrocardiogram of a ventricle of a heart of the subject, and an analyzing section that performs a frequency analysis on the intracardiac electrocardiogram and includes a range setting section that sets an analysis time range of the frequency analysis in the intracardiac electrocardiogram based on a unit waveform of the body surface electrocardiogram, and a calculating section that, in the analysis time range, performs the frequency analysis on the intracardiac electrocardiogram, and that calculates an index value indicating a ratio of local abnormal ventricular activities in the intracardiac electrocardiogram.
