Now we using purpose area rule of city planning code in city planning areas for efficient, economical use of land and increasement of common welfare. Architectural code restrict building purpose after each division of area and this aimed for making more comfortable and convenient living atmosphere in city environment. Through this research we extracted conclusion about purpose area distinction system and restriction of building purpose after examined changes and tendencies of these rules. And the conclusion is the changes of purpose area distinction system issued from 32 kinds of distinctions in 1978, 28, 30, 32 kinds of distinctions in 1992 to 21kinds of distinctions in 1999 are caused by demand of enabling different purposes of programs can exist within one building possible.