PURPOSE: To relieve the stress concentration in the toe of weld of beads and improve bending deformability by specifying the diameters of two wires, inter-electrode distance, and the relations between the respective shortest distance between a preceding electrode and a side plate and a succeeding electrode and the side plate in forming the final beads on a bottom plate.

CONSTITUTION: The fillet part formed by a side plate and a bottom plate is welded by using a submerged arc welding method. In forming the final beads on the bottom surface at this time, two pieces of wires of 1.6W3.2mm diameters are used, and these are used as a preceding electrode and a succeeding electrode. The interelectrode distance of the preceding electrode and the succeeding electrode is kept below 30mm, and the electrodes are held within a (a)+6mm≤b≤(a)+25mm range where the shortest distance between the preceding electrode and the side plate is defined as (a)mm and the shortest distance between the succeeding electrode and the side plate as (b)mm. Then, welding is accomplished in one pool, and the width of molten pool is increased, whereby the rising angle in toe of weld of beads is lowered. Hence, the stress concentration in the toe of weld is relieved.