Since 2018, the government of South Korea has strengthened its environmental policies to solve the problem of fine particulate matter in the air. Because of these strict regulations, diesel cars have been replaced with cleaner vehicles, and coal power plants have been shut down. Despite these government efforts, some researchers assert that fine dust programs have failed in Seoul, the capital of Korea. In other words, they conclude that the central and local governments designed and implemented the policies unreasonably. Despite these critics, this study attempts to prove that the government has thoroughly and meticulously prepared its policies on fine particles. Also, it tries to demonstrate that the policy scheme has been properly established. To attain these research goals, the theory of procedural rationality is adopted and utilized. As a result of the analysis, six steps of procedural rationality were identified in the Korean policy on fine dust: problem identification, goal setting, searching for alternatives, consequence prediction, comparison of alternatives, and policy decision. In conclusion, this study provides suggestions for environmental policies in other metropolitan cities, especially in developing countries that suffer from severe air pollution.