Film sound should be analyzed based upon the profound understanding of sound design process and the principle behind it. Lack of this knowledge prevents the research from having the comprehensiveness and concreteness. This study aims to reaffirm the important role of sound design in filmmaking while also investigating the narrative functions of sound design. The role of sound design as a cinematic technique was defined as creating audio-visual experience with a collection of information, emotion, and ideas organized and presented in the sound narrative of films. Each process of sound design, dialog, ambience, Foley, and sound effects, was proved to be performing this role as a result of a case study of various narrative films. The narrative functions of sound design was able to be defined as well.