To provide a solid wire for carbon dioxide shielded arc welding, the solid wire that enables sufficient penetration to be obtained even in a narrow groove execution and that enables weld metal to be obtained which is superior in mechanical performance such as strength and toughness.

The solid wire contains, by mass%, 0.03-0.10% C, 0.67-1.00% Si, 1.81-2.50% Mn, 0.006-0.018% S, 0.100-0.150% Ti, 0.0015-0.0070% B, and 0.10-0.45% Cu having solder content, with parameters PBS and PMT satisfying PBS10 and PMT32, controlling 0.020% P, 0.04% Nb, 0.04% V, 0.04% Al, with the balance being Fe and inevitable impurities, wherein PBS=[B][S]105 and PMT=[Mn][Ti]102.