There were regional increases and decreases in the number of farm households in pre-war Japan. The aim of this paper is to analyze relevant data of prefectures in the prewar period to find out the regional character of the changes in the number of farm households, and to examine its factors in relation to the Ie system. Our analysis drew six points of conclusion: (1) The number of farm households increased in eastern Japan and south Kyusyu, and decreased in western Japan; (2) Regional increase and decrease in the number of households correlated with the rise and fall in the number of tenant farm households; (3) Regional increase and decrease in the area of arable land also correlated with changes in the number of farm households; (4) Regional shifts in rural populations correlated with regional rise and fall in the number of farm households as well; (5) It is not a correct perception that impartible inheritance of land to a single heir dominated in prewar Japan. The reality was that many farmers divided their Ie property while they were still alive and gave small parts to children who did not succeed to their Ie; and (6) The number of farm households in eastern Japan grew due to the increase in the rural population and creation of tenants households that were given small tenant rights by the father as a social security in exchange for lack of inheritance of Ie.