This paper analyzes the entrepreneurial activities relating to market and product developments and the plant and equipment investments, and their contribution to the development of Yasukawa Electric Co. Yasukawa Electric Co. was established in 1915 as a part of the Yasukawa family's business diversification, initially producing generators, motors, and transformers. The company did not fare well in the 1920s, due to the slow product development and the formation of sales organizations. From the late 1920s, the product development focusing on motors became active. During the Great Depression, the production became organized around electric motors and the sales network expanded. Thus the company grew rapidly in the 1930s. The establishment of the mass production system stemmed from the active plant and equipment investments beginning in 1933. These developments were made possible by the increasing influence of salaried managers. The advent of salaried managers and their supporting staff necessitated an adjustment of interests in the Yasukawa family's businesses, and changed the process of decision making in the Yasukawa family as well.