This paper examines the relationship between Korean electric power industry and American oil companies by researching the generation expansion planning and entry of American oil companies into the Korean electric power industry during 2nd 5-Year Economic Development Plan. The government promoted energy policy based on fuel oil and promoted large-scale generation expansion planning by the establishment of private power companies separate from Korea Electric Power Company. Under this background, American oil companies built private power plants and entered Korean electric power industry. However, the ultimate goal of American oil companies to enter Korean electric power industry was to enter and secure the Korean oil market. In particular, Union Oil was able to advance into the Korean oil market by constructing an oil refinery to supply fuel with the power plant. Korea Electric Power Company and private power companies were linked to American oil companies through long-term fuel oil contracts and loan contracts. Under long-term fuel oil contracts, Korea Electric Power Company was able to secure stable fuel supply and loans, and American oil companies were able to secure stable profits by exercising their exclusive rights to supply fuel. However, Korean electric power industry eventually has been affected by world oil market as a result of the dependence on American oil companies.