To the arctic off-shore structures under huge ice load, it is very interested to apply the composite steel-concrete beams, where concrete is filled between steel plates, as the exterior walls of the structures. In this paper, the authers carried out static loading test to investigate the strength of the composite steel-concrete beam in the various cases, they are load distribution, span length, size of supporting plate, beam end condition, shear connector and web plate. The main conclusions are as follows; (1) The strength of the beam under a symmetrical load to mid-span is greater than that of symmetrical load. (2) The length of supporting plate placed under the beam have considerable influence on the strength and deflection of the beam. (3) Where the ratio of span to depth of the beam is 2.0, influences upon the beam strength by end condition are negligible and decrease of the ultimate strength in the case of no shear connectors or no web plates is not found. (4) The calculated ultimate strength by Niwa's formula for reinforced concrete deep beam is in good agreement with experimental ones.