The invention provides a start welding method for two-wire welding, wherein a welding line with enough bonding strength is formed after welding starts. Electric arc (2A) is generated from a wire (WA) as a wire (WB) is fed to the wire (WA) from back along the welding direction, which comprises a step of welding by electric arc (2A, 2B) and a step of welding only by electric (2A) through quenching the electric arc (2B). Enough heat is transferred to welding base metal (P) after welding starts so that enough width is provided at the beginning end of the welding line (Wp).