A method of manufacturing a semiconductor device includes: (A) providing a wafer to which a photo-resist is applied; (B) forming a reacted portion in the photo-resist by exposing the wafer to a light through a mask having a translucent section, the reacted portion being a portion reacted with the light; and (C) forming a resist mask having an opening portion corresponding to the translucent section by dissolving the reacted portion. The opening portion does not penetrate the photo-resist in a case where an exposure amount in the (B) process is a first exposure amount. On the other hand, the opening portion penetrates the photo-resist in a case where the exposure amount is a second exposure amount larger than the first exposure amount.