This paper studies Japanese engineering contractors in the colonized Korea (then Joseon). The Japanese Government General of Korea enabled Japanese contractors to secure profits. Korean workers were working for those Japanese contractors at low wages. Japanese contractors often omitted the payment of the low wages, and the issue of unpaid wages was being reported on newspapers. According to the official statistics of the Japanese Government General of Korea, despite some differences between periods, the wages of Korean workers were about 1 yen a day per person, which was almost half of the wages of Japanese workers. However, the actual wages of Korean workers were 30 through 50 Jeon (a hundredth part of one won), which was only a quarter of the wages of Japanese workers. Though the estimate of bid was calculated with the wages of Korean workers as 1 yen, actually 30 through 50 Jeon were paid to them. Thus, the difference was being legally exploited by Japanese contractors. Some data say that back then labor cost accounted for about 57% in civil engineering projects, and Japanese contractors were exploiting more than half of that. Since this was a structural problem, is was a problem applicable to almost the public works (accounted for 1.07 billion yen) of the whole period of colonial days.