For the presentation of spatial features in various thematic map types, the optimal preservation of the shape, ratio of area, directions are one of the major design principles. "Cartogram" is an exception. Although in the application of "cartogram" , recognition of the spatial features is an important factor, the size of the features varies with the value of the attribute in the thematic map. When it is properly applied, "cartogram" provides better information dissemination and transformation efficiency. This paper introduces the basic principle and theory of "cartogram" utilizing illustrations of election results. An example of the presidential election in the United States and four presidential elections in Taiwan are utilized to demonstrate the application and limitation of "cartogram".