To provide a method for improving the adhesive properties between rubber and a brass plated steel wire for reinforcing a rubber materialusing a benzotriazole based or benzoimidazole based compound used as working oil for copper and a copper alloy.

When a steel wire rod whose surface is subjected to brass plating is subjected to wet wire drawing using an emulsion type lubricant comprising an extreme pressure lubricating component and an oily lubricating component, the wire drawing treatment is performed using an emulsion type lubricant in which the content of the extreme pressure lubricating component is controlled to 0.1 to 2.5 wt.%, the content of the oily lubricating component is controlled to 0.2 to 5.0 wt.%, further, as a rust preventive serving also as a surface improving agent, a benzotriazole based or benzoimidazole based compound is comprised by 0.3 to 1.0 wt.%, and also, ZnDTP as an extreme pressure additive is comprised by 0.1 to 1.0 wt.%.