PURPOSE: To provide a composite body of a steel cord and rubber better in the rubber penetrability without the generation of rust, fretting phenomenon and the lowering of the wear resistance by depending on specified values in the air permeation and the shortest distance between strands adjacent to each other in the outermost layer as calculated from a specified expression.

CONSTITUTION: When a steel cord is covered with rubber by permeation, working is performed to satisfy requirements of less than 70cc/min in the air permeation V and 0.017W0.1mm in the shortest distance GAP between strands 1 adjacent to each other in the outermost layer to obtain a molding as calculated by the formula I [V represents air permeation(cc/min) of steel cord; n the number of strands in the outermost layer of the steel cord; MV Mooney Viscosity of rubber blended; CG diameter (mm) of circumscribed circle, GAP the shortest distance (mm) of strands adjacent to each other of the outermost layer of the steel cord; P the largest pressure (kg/cm2) at the production of composite body and T50 measured value (min) of rubber blended with an oscillating disc rheometer curemeter] and the formula II [d represents the diameter of strand (mm) in the outermost layer of the steel cord and D diameter (mm) of circumscribed circle with the outermost layer of the steel cord].