A steel wire (e.g., a piano wire) for use in a stringed musical instrument is designed to have a specific chemical composition in which phosphorus content ranges from 0.015 weight percent to 0.050 weight percent, wherein the total decarburized layer depth of a decarburized layer formed on the surface, which is subjected to decarburized depth measurement using a microscope method as defined in the Japanese Industrial Standard JIS G 0588, is reduced to 2 .mu.m or less. Other chemical substances included in the chemical composition of the steel wire are preferably defined in the standard JIS G 3502 regarding chemical compositions of piano wires. In manufacturing, a rolled steel material is subjected to wire drawing and patenting under prescribed conditions, wherein the sound quality realized by the steel wire installed in a stringed musical instrument can be noticeably improved by adopting both chemical composition control and total decarburized layer depth control.