By using simple model, diffusion process of the new products of clothing was analysed. The model was set up on the following two assumptions; (1) new products would be used for a long period, (2) the influence of the users of these new products upon the other people's purchase desire would be always equal. Using this model, variation of the number of people with elapsed time, who had bought this new product, was analysed. Then some equations related to diffusion process of the new products were derived. According to these equations, it was appeared that; (1) N(t)/M, the diffusion rate curve of the new products, formes S-shape curve, so-called logistic curve, (2) F(t)/M, curve of the number of people who buy the new products in a unit time, forms bell-shape curve, which is similar to the normal distribution curve.Shapes and values of these curves are determined by the value of coefficients α and k. Coefficient α relates to the influence of the users of the new products upon the other people's purchase desire, who have not bought this new product yet. As α increases, the diffusion speed becomes faster. Coefficient k relates to the number of people who possess these new products at the beginning of the sales. As k increases, diffusion of the new products requires long time. For bigger k, the curves of N(t)/M and F(t)/M move to right on the graph, but their shapes do not change.