Disclosed is a solid wire for gas shielded arc welding treated with a surface treatment soil which includes metal salts containing Sodium (Na), potassium (K), calcium (Ca) and zinc (Zn), and a non-metal phosphorus (P), and a hydrocarbon compound containing at least two functional groups selected from the group that consists of ester, carboxylic acid and alkane groups. According to the present invention, the solid wire treated with a specific liquid surface treatment agent exhibited superior rust resistance and wire feedability to those of conventional solid wires.