A first resist film is irradiated with first exposure light and performing first development, thereby forming a first pattern in a first region including an interconnect trench pattern and forming a dummy pattern in a second region connected to the first region and having a pattern density lower than that of the interconnect trench pattern. Then, the first resist film is hardened, and a second resist film is formed on the hardened first resist film. After that, the second resist film is irradiated with second exposure light and performing second development, thereby forming a second pattern in the first region. When forming the second pattern, an opening made of the first pattern and the second pattern and including the interconnect trench pattern is formed in the first region, whereas in the second region, an opening in the first dummy pattern is filled with the second resist film.