We study the historical changes of the numerical values appeared in the regulations for structural calculation. The regulations and their drafts, from the Drafts of Tokyo City Building Ordinance planned by members of A.I.J. to the Urban Building Law Enforcement Regulations, aresurveyed in this study. The foundations of their changes are our main interests, too. The results are as follows : 1) The later regulations were more detailed than the Drafts of Tokyo City Building Ordinance. But, it caused bigger damages by the earthquake that some texts of these regulations had been relaxed. 2) The values and their units are not the same in each of the drafts, on the regulations about the live load and what was called the allowable unit stress of materials, because planners had changed and mistaken in writing. 3) The regulations about the live load and the allowable unit stress of materials were influenced mainly by the Building Code of the City of New York, partially by the material experiments in Japan. Also the foreign regulations were referenced to the other value regulations. 4) The value of the wind pressure regulations were based on the weather records.