To enhance improvement in quality of a welded structure, high efficiency at a welding site, and reduction in the cost by using a rutile type flux cored wire whose diameter is in a specific size range, setting a specific distance range between the tip and a base material, and performing fillet welding at a specific welding speed or above.

A distance ML between a welding tip and a base material is set at 35-50 mm. At less than 35 mm, preventive effect is not fully demonstrated against welding deformation and pit which are due to penetration depth of a bead. On the other hand, at more than 50 mm, the aiming position of a wire 3 is not stable, causing disturbance at a bead toe or generating spatters that are likely to stick to a steel plate 1. A high deposition performance is required for the purpose of preventing undercut that tends to be generated in accordance with high speed; therefore, the wire diameter is designed to be 1.2-1.6 mm, a fine diameter capable of accelerating a wire melting speed. Further, fillet welding is performed at a welding speed ≥0.8 m/min.