A visualization apparatus includes a storage unit and a computation unit. The storage unit stores a three-dimensional model of a heart, excitation propagation data indicating temporal variations of electrical signal strength in myocardium during propagation of excitation in the heart, and infarct area data indicating locations of infarct areas in the heart. The computation unit places a measurement point on an accessory pathway between the infarct areas. Then based on the excitation propagation data, the computation unit determines a variation range of electrical signal strength as a range between its minimum and maximum values at the measurement point. The computation unit outputs a picture that visualizes propagation of cardiac excitation in the three-dimensional model, based on the excitation propagation data, by varying a visual property in the picture to represent variations of the electric signal strength within the determined variation range.