The mixed structures composed of reinforced concrete (RC) columns and steel (S) beams are effective for long spans. Lots of beam-column joint details have been developed. These joints need particular arrangements to transmit stresses between S-beams and RC-columns. In addition, the concrete casting may be inefficient to construct dense concrete joints. The hybrid beams that consist of RC beam-ends and S beam-center could be practical instead of S beams, because beam-column joints may be constructed in pre-cast concrete members. There are some researches on the hybrid beams. In many cases, those H-shaped steel beams are embedded in reinforced concrete beam ends, and large leverage shear stresses are occurred at the connections. Authors have proposed new connecting way for the hybrid beams, utilizing the boundary steel plate between RC and S-beam instead of the way embedded steel in RC-beam. This paper reports the stress transforming mechanism of new method and the test results of the proposed hybrid beams.