A geometric model of an organ represents its shape as a collection of elements formed from nodes and connections among them. A first vessel network model represents a network of first vessels whose diameters are larger than or equal to a threshold. A plurality of second vessel networks each represent a network of second vessels whose diameters are smaller than the threshold. In a simulator apparatus, a first analysis unit analyzes hemodynamics in the first vessels, based on the geometric model and first vessel network model of the organ and reflecting the motion of the organ. A second analysis unit analyzes hemodynamics in the second vessel network models connected to the nodes, by using output data of the first analysis unit which indicates the hemodynamics in the first vessels at each of the nodes.