Patent ID: 7287683

Claim:
A friction stir welding method of a panel to a plate member, wherein: said panel comprises a first plate, a second plate substantially parallel to said first plate, plural ribs for connecting said first plate and said second plate, and a vertical plate for connecting an end portion in a width direction of said first plate and said second plate and being substantially perpendicular to said first plate and said second plate; and a connection portion between said first plate of said panel and said vertical plate, providing a recessed portion which opens in a thickness direction of said first plate of said panel and in a direction perpendicular to said thickness direction; arranging an end portion of said plate member in said recessed portion; and friction stir welding an overlapped portion of said end portion of said plate member and said recessed portion of said panel from an outer side of an extension line of a plate thickness of said vertical plate of said panel.