Heart failure diagnostic device

Provided is a novel heart failure diagnostic device capable of performing high-precision diagnosis of heart failure based on respiratory stability on the basis of the detection results of a flexible piezoelectric sensor sheet that does not need to be worn on a user. A heart failure diagnostic device (10) diagnoses heart failure using an index generated on the basis of the standard deviation of the respiratory rate of a user (P), the heart failure diagnostic device (10) comprising: a flexible piezoelectric sensor sheet (12) that outputs a detection signal in accordance with input vibration; a respiration signal acquisition unit (40) that extracts, as a respiration signal, a signal of a vibration frequency caused by respiration from a detection signal of the piezoelectric sensor sheet (12); and a power spectrum calculation unit (44) that calculates the power spectrum of the respiratory band on the basis of the respiratory signal, the heart failure diagnosis device (10) being provided with a signal correction un