Evidence for bulk superconductivity in Nb2SC0.90 carbosulfide is presented. Diamagnetic volume fraction of Nb2SC0.9 was precisely determined with low applied magnetic fields which were corrected by 6N lend rod as an internal standard. Based on magnetic field dependence of magnetic moment at several constant temperature's below T-C = 5 K, Nb2SC0.9 is found to be a type II superconductor with relatively high H-C2 and low H-Cl.