A coil spring modeling apparatus includes a first attachment member disposed on a lower spring seat, a second attachment member disposed on an upper spring seat, an actuator unit formed of a Stewart-platform-type parallel mechanism, a hydraulic pressure supply device, a torsion detection mechanism, and a controller. The torsion detection mechanism is constituted of displacement gauges such as a linear variable differential transformer. The displacement gauges are provided on hydraulic cylinders, and detect amounts of displacement relative to the reference lengths of the hydraulic cylinders, respectively. The controller calculates a relative torsional angle between the first attachment member and the second attachment member based on the detected displacement.