There are two theories to estimate the ultimate torsional strength of reinforced concrete members. One is space truss theory and the other is skew-bending theory. On the space truss theory it is convenient to derive the equilibrium and kinematric conditions and to develop the research of reinforced concrete member subjected to combined torsion and bending. This paper is an attempt to clear the torsional resistance of reinforced concrete members based on the space truss model. It is assumed that the angle of direction of cracking will be fixed so that shear strain is minimum. The three patterns of the failure by longitudinal bar, transverse hoop bar or concrete struts are determined by the conditions of the angle of cracking. From the results of the comparison of experimental and theoretical torsional resistance, the proposed theory is shown to be available.