Based on the existentialistic concept for the existence of a human being, the relationship between the freedom inherent in a human being and engineering is studied in this paper, taking into account two representative examples of engineering subjects; i.e., design and environmental systems. As a result, the ability to create originality avoiding conventionality, the essential motive of leading us to new ideas, and the inevitable limit of the engineering analysis of human activity have been clarified as to how and where they are brought about or exist in connection with the existence of a human being.