The purpose of this study is to present an improvement building construction process by using prefabricated materials. The current slab form work has waste factor by unnecessary process and not complete integration with the finishing process. Therefore the study used value stream analysis methodology for effective improvement of slab form work process. The main contents of the study are as follows; 1) Non-value adding activities were found at existing slab form work process by current state mapping(CSM) 2) Future state mapping(FSM) suggest process Integration to slab form work. 3) Slab form work is analyzed reduction time-cost by prefabricated material. The study recommends that, as a future research, development of tool and technique for the non-value adding activities are eliminated in building construction and application of prefabricated material should be increased.