The Ferro-Concrete structure technology was introduced into Japan in 1890s. In this paper, we try to show that a purpose of the spread played an important role for introduction of Ferro-Concrete in Japan. Various calculation formulas and sign of Ferro-Concrete ware introduced into Japan passing many separated ways and coexisted. It is thought that when it establish a law in 1920 and standardized Ferro-Concrete structure technology, economical conditions would be considered for the spread of this technology. However, the policy for the spread was changed by the damage of Kanto Earthquake(1923). And a deformed bar against the policy of the spread was removed at that time. It is thought that the introduction of Ferro-Concrete would be typical example of process to introduce new technology in Japan.
