A solid wire is for gas-shielded arc welding, using a shielding gas, and for galvanized steel sheet welding. The solid wire comprises, to the mass of the whole of the solid wire, predetermined amount of C, Si, Mn, P, S, O, and Cr, with the balance consisting Fe and inevitable impurities. The solid wire satisfies “1.0≦(percentage by mass of Si+that by mass of Mn)/{100(that by mass of S+that by mass of O}≦4.0” and “0.50≦percentage by mass of Mn/that by mass of Si≦2.00”. The shielding gas is an Ar gas comprising 25 to 40% of CO2 gas. It is achieved to improve spatter-decreasing performance and pore-resisting performance (performance of restraining the generation of porosity defects, such as pits and blowholes).