An animal model is provided which can be used for testing efficacy of a drug on left ventricular myocardial diastolic dysfunction, for example heart failure due to left ventricular diastolic failure. The present invention resides in a method for preparing an animal model with left ventricular diastolic dysfunction for testing a therapeutic agent for heart failure, the method comprising: intravenously injecting an aqueous solution of a water-soluble calcium salt into an anesthetized experimental small animal; and intravenously injecting an aqueous catecholamine solution into the animal, while continuing the intravenous injection of the aqueous solution of the water-soluble calcium salt, to raise left ventricular end-diastolic pressure of the heart of the animal to a level higher than normal left ventricular end-diastolic pressure, and it also resides in a method for preparing an animal model with left ventricular diastolic dysfunction for testing a therapeutic agent for heart failure due to left ventricular diastolic failure, the method comprising: intravenously injecting an aqueous norepinepfrine solution into the animal model prepared by the former method; measuring left ventricular end-diastolic pressure; and comparing the measured left ventricular end-diastolic pressure with normal left ventricular end-diastolic pressure of before the injection of the aqueous norepinephrine solution.