PURPOSE: To prevent the variations in heat treatment effect for the entire part of the steel wire materials and obtain the homegeneous steel wire meterials by forming the steel wire materials in waveforms in their lengthwise direction, bundling these in coil form and subjecting the same to heat treatment.

CONSTITUTION: Steel wire materials are formed to waveforms like Fig. A, Fig. B or Fig. C in their lengthwise direction by using the corrugating rolls attached to, e.g., existing finishing mills. Next, the steel wires having been formed to waveforms are bundled in such a manner that the directions of the respective steel wires and the position of waves become random, after which they are subjected to heat treatment. This heat treatment is accomplished by banding together a suitable number meeting furnace capacity, etc. as a unit in accordance with ordinary methods, and setting the suitable heat treatment conditions to be employed depending upon the kinds of steels, sizes, applications, target quality, etc. of the wire materials. This method makes it possible to give suitable voids among the steel wire materials with each other and effectively prevent local temperature differences in the heating and cooling course in varuous heat treatments.