The writer shows in this paper the stages of development foundry industry of Sanjo: (1) The foundry dependent on handicraft of the farmer's side job. (2) Emergence of the foundry craftsman as a specialist. (3) The first stage of the foundry under the control of the wholesale merchants. (4) The second stage of the foundry under the control of the wholesale merchant. (5) The modernized and concentrated foundry. In the developing stage of the Shogunate Era the foundry craftsmen obtained their materials of products from the wholesale merchants and the deal of their products were under the control of the wholesale merchants. Afterwards the wholesale merchants gave craftsmen the fund to obtain materials. The production and dealing system changed gradually, but remarkable change came after the 2nd World War. The control of the wholesale merchants quickly disappeared since then, and modernized factories were built. Concentration of the factories was the new trend. In spite of modernization, the foundry industry of Sanjo are all the small scale one in both capital and factory even today. The kinds of products which are produced in the different factories are very various and each amount of products is not much. In addition the technical process still depends mainly upon handicraft, most of them are combined each other through various kinds of technical processes. It is one of the reasons why concentration are promoted.