To easily cope with the change of a model, an analysis expression, etc., by performing simulation when a flow except a basic flow occurs by utilizing a flow dividing part which simulates partial flow division of a liquid and a confluent part which simulates confluence of plural liquids.

Object type software that separates an operation in each base element and calculates is utilized, and also a mixing part simulates the mixture and separation of two phase liquids and the mass transfer between the two phase liquids as a base element that constitutes an extracting device. Further, a flow dividing part simulates partial divided flow of the two fluids, also a confluent part simulates the confluence of plural liquids, and simulation when a flow except a basic flow occurs as an element model for calculation of equilibrium density and mass balance is performed by using the flow dividing part and the confluent part. Consequently, it is possible to easily cope with the change of a model, an analysis expression, etc.