The purpose of this study is to examine the construction industry of Korea from the 1920s to the 1930s by analyzing activities of construction-contractors trying to overcome the recession of the construction industry and intensified competition in the industry. In this paper, I looked at the activities of Hanazono Sakichi as concrete examples. First of all, with the strategy of the vertical integration, by manufacturing and selling building materials, Hanazono Sakichi expanded his company and the scope of contract business. The second, he attempted to diversify related projects. Through related diversification, he seemed to have earned not only land management profit but also advantages from related construction. These aspects were not only seen by Hanazono’s activities but also by other contractors’. On the other hand, a few contractors have taken over a trust company to secure the funds for land management. Attempts to maximize personal interests through the expansion and diversification of contractors' business can be seen as overcoming the pre-1920s environment, where almost construct works were ordered under the government, and creating opportunities for the private sector to work and make profit by themselves. In the end, it can be mentioned that ‘the contractor’ established ‘the construction industry’ through this process.