The rate of frequency of labor accident occurrence is generally used as one of the expressions of labor accident, which is defined as the rate of number of labor accidevits to one rrrillion laboring men hours. In Japan this rate frequency announeed ofrilcially by the Ministry of Labor is based on the data of 15000 industries where labors more than 100 are employed. However, as the rate of labor acci dents in small scale industries is generally larger th~n that in largo sc_ale ones, the rate of frequency announced ofrlcially cannot be said to stand for that for all labors employed and for all industries of any scale, In this reseairch the author has tried to obtain the rate of frequency of labor accidents for any scale industry and its yearly change in accordance with the data annotinced officially. The equation ob tained can estimate the effect of small scale industries on the fotal rate of frequency of labor accident. which differs, for example In 1981, 3,3 times from the offlcial data.