A visualization apparatus, comprising: storage means configured to store a three-dimensional model of a heart of a patient, heart behavior data representing shapes of the heart at different time steps of a behavioral simulation of the heart, and electrocardiogram data representing temporal variations of an electrical signal in myocardium that have been measured from the patient; and computation means configured to determine a first time step at which atriums of the heart begin to contract, as well as a second time step at which ventricles of the heart begin to contract, based on the heart behavior data, and reproduce behavior of the heart over time by updating the three-dimensional model according to the heart behavior data, simultaneously with variations in strength of the electrical signal over time according to the electrocardiogram data, such that a first shape of the heart at the first time step is reproduced when the electrical signal reaches a peak of a P wave appearing in an electrocardiogram, and such that a second shape of the heart at the second time step is reproduced when the electrical signal reaches a peak of an R wave appearing in the electrocardiogram, wherein: the computation means is configured to divide a single heart beat cycle into first to third sections, the first section being a period from a start of the electrical signal that initiates the single heart beat cycle to a peak of the P wave, the second section being a period from the peak of the P wave to a peak of the R wave, the third section being a period from the peak of the R wave to an end of the electrical signal that terminates the single heart beat cycle; and the computation means is configured to determine at what constant time intervals the computation means is to reproduce the shapes of the heart at different time steps, depending on to which of the first to third sections of the single heart beat cycle the different time steps belong. storage means configured to store a three-dimensional model of a heart of a patient, heart behavior data representing shapes of the heart at different time steps of a behavioral simulation of the heart, and electrocardiogram data representing temporal variations of an electrical signal in myocardium that have been measured from the patient; and computation means configured to determine a first time step at which atriums of the heart begin to contract, as well as a second time step at which ventricles of the heart begin to contract, based on the heart behavior data, and reproduce behavior of the heart over time by updating the three-dimensional model according to the heart behavior data, simultaneously with variations in strength of the electrical signal over time according to the electrocardiogram data, such that a first shape of the heart at the first time step is reproduced when the electrical signal reaches a peak of a P wave appearing in an electrocardiogram, and such that a second shape of the heart at the second time step is reproduced when the electrical signal reaches a peak of an R wave appearing in the electrocardiogram, wherein: the computation means is configured to divide a single heart beat cycle into first to third sections, the first section being a period from a start of the electrical signal that initiates the single heart beat cycle to a peak of the P wave, the second section being a period from the peak of the P wave to a peak of the R wave, the third section being a period from the peak of the R wave to an end of the electrical signal that terminates the single heart beat cycle; and the computation means is configured to determine at what constant time intervals the computation means is to reproduce the shapes of the heart at different time steps, depending on to which of the first to third sections of the single heart beat cycle the different time steps belong. the computation means is configured to divide a single heart beat cycle into first to third sections, the first section being a period from a start of the electrical signal that initiates the single heart beat cycle to a peak of the P wave, the second section being a period from the peak of the P wave to a peak of the R wave, the third section being a period from the peak of the R wave to an end of the electrical signal that terminates the single heart beat cycle; and the computation means is configured to determine at what constant time intervals the computation means is to reproduce the shapes of the heart at different time steps, depending on to which of the first to third sections of the single heart beat cycle the different time steps belong.