My thesis is basically about the concept of architecture, where humans, regarded as a living machine, will lead their lives in the future. This thesis aims to develop solutions to the problems (CO2, population, social level, sprawl phenomenon, and so on). I pictured the image of Laputa Island in Gulliver's travels in order to solve problems of the city. This is the definition of the Laputa. (Laputa: Floating island in the sky, mentioned in Gulliver's travels) Lebbeus Woods showed imaginary architecture in the future, which mentioned "floating housing" in his works such as "Aerial Paris," "Havana Project," and "High House." In short, the scale of cities will be expanded horizontally and vertically. However, people cannot only swarm about contemporary cities, due to their adjacency, movement (traffic), and limited time. The flow of many people into cities expands cities and creates many inevitable social problems, and naturally destructing cities. While deliberating on solutions to the destruction, I draw the basic hypothesis of floating housing from the works of Lebbeus Woods to bring about the reconstruction of cities. The type of floating housing represents the animals living in the existing buildings. I define such buildings as parasitic housing. Stress is laid on the adjacency of parasitic housing, which is plugged into the original architecture. I focus on the structure of parasitic housing in order to design realistic parasitic housing. All the materials of parasitic housing are pre-fabricated, so they may be easily constructed, and enormous truss structures are set up so they may support the entire load and exterior of the buildings. Last year, when I prepared for this thesis, based on such a basic concept of architecture, I made efforts to suggest future city problems and architectural solutions to them by appling with my own architectural color. Basically, my thesis is divided into two chapters. In each chapter, I endeavor to communicate my architectural language to my readers. The first chapter presents the basic theme of my thesis or the definition of prefab architecture, which is unfamiliar to the readers, and prefab architecture movements in each age. Research is also completed regarding the relationship between society and culture. The second chapter presents solutions to future city problems in an analytical (numerical) manner and resolves the problems through applying a case study to my work.