PURPOSE: To stably obtain a high fatigue strength joint in over the wide range regardless of any kind of steel material, welding material and welding method by forming the welded joint, in which a rib plate is welded with a boxing to a main plate, to a prescribed dimensional shape.

CONSTITUTION: Firstly, a corner boxing part 3 is welded and this welding length L1 is longer by (2 × fillet welding foot length) or more than (rib plate thickness + 2 × fillet welding foot length). Successively, the fillet welding part 4 along the rib plate 2 is welded toward the corner boxing part 3. When the welding position contacts with the corner boxing part 3, the welding 4a to the direction being apart from the rib plate at the right angle direction to the rib plate 2 is executed. Then, when the welding position is apart from the surface containing the rib plate 2 by ≥30mm, the welding direction is changed so as to become the parallel to the rib plate 2, and the welding 4b being apart from the rib plate in the parallel to the rib plate. The whole length L, of the welding in the parallel to the rib plate is made to be longer than the half of the width of the main plate 1. In the other welding (5→5a→5b) is executed as this same way.