A new type of frame structure composed of steel beams and reinforced concrete columns is proposed. The concrete in the beam-column connection is confined by thin steel plates called "cover plate". Shear capacity of connectionis investigated experimentally. Thirteen specimens of interior column-beam assemblage and four specimens of exterior column-beam assemblage were tested. The shear forces acting in the connection are resisted by the steel web panel and the concrete panel and the cover plates. The effective length of the steel web and the cover plates were determined from test results. An equation of the effective width of the concrete panel in the connection is proposed.