An elastic sheet is defined in accordance with a user input operation to have a shape with which the elastic sheet does not cross another member (building component) (step S1). Then, the elastic sheet is divided into rigid elements (step S2). Angles formed by each rigid element with adjacent rigid elements on two sides are calculated, and the calculation results and the like are stored in a RAM (step S3). A flexible medium which moves through a conveyance path is defined (step S4). Conveyance conditions when the flexible medium moves through the conveyance path are set (step S5). After that, the motion is calculated (step S6). The result of the motion calculation, that is, the behavior of the flexible medium, is displayed on a display device (step S7).