A design methodology of both space structure beam and construction robot is described from the point of total cost minimum. The study is experimentally investigated. At first, two types of beams are prepared. One is a deployable truss structure. This truss is stowed in a rocket fairing folded, and is then deployed in orbit. The other is a putting-pipe-in-socket type beam in which members are separated from the beam, and then these are put in joints in orbit. In this paper secondly, ground experiment on beam construction with an industrial manipulator system are reported. The experiment proves that the dual arm system can conduct both types of beam. Furthermore, it obtains useful system requirements for structure beams. In conclusion, a design of both space structure beam and construction robot is proposed.