A steel cord that is especially useful for reinforcing a crown portion of a tire is provided. In particular, a steel cord free from manufacturing problems existed in the conventional art and allowing for stable quality and good production efficiency is provided, and a rubber-steel cord composite and a tire that are equipped with the same are provided.A steel cord has a multiple-twist structure including N (N=2 to 8) strands 2 that are twisted together, each strand 2 having a plurality of wires 1 that are twisted together. When the diameter of each strand is denoted by d (mm), the diameter of a circle circumscribing the cord is denoted by D (mm), and the twisting pitch of the cord is denoted by P (mm), εc defined by the following expression, εc=√(−b/2+√(b2/4−c))−1 (where b denotes −1+π2(−4R2+d2)/P2, c denotes π2d2k(4π2R2+P2)/P4, R denotes (D−d)/2, and k denotes tan2(π/2−π/N)), satisfies εc≧0.005.