Since the Nobi Earthquake of 1891, seismology, engineering seismology, earthquake engineering, structural engineering and sciences which are related to the phenomena of earthquakes were developed in Japan. Especially pure sciences and engineering made great advances individually. However, actual earthquake damage has not yet ceased to exist, and this damage leads the loss of a great number of human lives. Undeveloped areas and not so important buildings have always suffered these disasters. From worldwise point of view, there is a more serious problem, sometimes more than 10,000 people are killed by an earthquake. The importance of these sciences and engineering is centered in such problems, but at their present stage of development they can not solve these serious problems. Primarily because there are many problems regarding the economical conditions. Seismic microzoning has its purpose in the solution of the serious problems mentioned above. The results of seismic microzoning should cover whole areas and structures, for saving money in construction and to minimize the danger posed to human life. Also seismic microzoning works are related to the disaster prevention programs of various areas. Investigations into seismic microzoning are mainly related to the field of engineering seismology and its applications are in earthquake engineering, but fundamental investigations and applications can not be separated, they are closely related. Thus difficult points still exist, because only a few investigators have interests in the applications of seismic microzoning work. In this paper the author tries to explain the theoretical background and the technique of application of seismic microzoning which developed mainly in Japan. But these theoretical and technical results are not yet completed, and the facts interpreted from the strong motion seismograms and other results of field observations will correct these conclusions.