The main purpose of this study is to examine the recent level of fertility and potentiality of the Korean population in Japan and to investigate some forces which influence the fertility of them using survey data. Some estimates of the level of fertility for the Korean population in Japan in 1974 are presented in Table 1. Comparing the some estimates for 1974 with those for 1969, the level of fertility in 1974 was realistically declined. It also indicated that potentiality of Koreans in Japan showed decreasing population. For investigating some factors affecting fertility, total births is selected which regressed on some variables believed in general to be influential in determiaing fertility. It was used a step-wise multiple regression to determine the independent as well as the combined effects of each of the variables. The SPSS computer program was used to perform the anlysis. Result from this data reveals that wife's family size preference as relevant predictor does influence the fertility of Koreans in Japan at this point considering that the age group of 20-29 is very much related. By employing multiple classification analysis, the analysis is concluded by nothing that the wi 3 family size preference has an even stronger relationship with economic factors than any other facto 3.