In this study, the fast numerical computation method by using simplified momentum equations, which exactly clarified the flow state inside a slot die, was developed, in order to obtain higher coating quality. The computation results elucidated the dependence of the uniformity of coating thickness on non-Newtonian characteristics. In addition, it was found that the computational procedure enables us to seek the optimum internal figures of a slot die immediately. The method was extended to a variety of rheological models, such as Power-Law, Ellis and Hershel-Bulkley model. As a result, the computation technique industrially contributed to the development of precise coating productions, such as optical elements, semiconductor and LCD display components.