During the 20th century, the economy of Japan has been developing at high rates. Major changes were have been witnessed in her industrial structure and capitalistic system. Nevertheless, the agricultural sector has been maintained as a family-run system. Based on a series of thesises I would propose that we should reconsider the theory of agricultural economics. 1. The family farm has two characteristics. Firstly, it is a commodity production business and secondly, it is a living unit as a family. In theory we can separate these two characteristics, but in practice they cannot be separated from each other. 2. The purpose of the capitalistic business is to make profit, precisely endless profit. On the other hand, the purpose of the family farm is to generate income enough for meeting living requirements, and to have a good life. This simple difference between the two is quite important in reconsidering our theory 3. Together with the economic development, the capitalistic logic carries through mostly in the social domain and in the private life. However, we cannot look at our life merely on the basis of the capitalistic logic. There is a different rule in our real life and thus it would be a big mistake to look at a family farm on the basis of the capitalistic logic only. A difference of logic between the capitalistic enterprise and family farm is as the same as the difference of logic between a legal person and a natural person. Compared with a legal person, a natural person has more sustainable behavior, and has a heart of living thing. 4. In fact, it is getting more and more difficult to use the fields available and to maintain the family farm. Nevertheless, we cannot think of continuing the development of agriculture without family farm because a capitalistic enterprise cannot carry out agricultural activities even if a family-run business does not carry them out. Therefore, a policy to support family-based farms is badly needed. If such a policy is in place, we can be optimistic about the future of a agriculture with family-based farms.