present invention an input device 26 such as a mouse keyboard and the like a display 27 that displays computational situations and results memories 28 29 such as rom and ram and a coating device 17 constituting a fluid structure body shown in fig3 and to which the coupled numerical simulation is implemented the host cpu 25 controls the coating device 17 input device 26 display 27 and memories 28 29 via a bus 30 fig6 shows computational procedures of the host cpu 25 when simulating the coating device shown in fig3 and 4 in fig6 at step st 1 initial settings and boundary condition settings and the like are implemented regarding the film 18 a film moving computational area of the moving object area 24 shown in fig4 a tension t of the film 18 and a feeding velocity of the film 18 and the like are set the mesh division is implemented by the infinite volume method using a known orthogonal mesh and a solid rate for each mesh and a position of each mesh in the tangent direction that show a flow state of fluid are set at the next step st 2 the settings regarding a position shape velocity boundary in the tangent direction of the film 18 are implemented at step st 3 fig7 a shows the state of mesh division at the portion corresponding.