JOINT STRUCTURE FOR STEEL PIPE PILE

A joint structure for a steel pipe pile in which a first steel pipe pile having an outer fitting end part and a second steel pipe pile having an inner fitting end part are coupled while the outer fitting end and the inner fitting end share the same axis center line, wherein when viewed in cross-section along the axis center line, outer fitting step parts (or inner fitting step parts) are providedat multiple positions along the axis center line on the inner side (or the outer side) of the outer fitting end part (or the inner fitting end part), so as to gradually increase (or decrease) in diameter toward the second steel pipe pile (or the first steel pipe pile); each outer fitting step part (or inner fitting step part) has an outer fitting crest part (or inner fitting crest part) relativelynear the second steel pipe pile (or the first steel pipe pile), and an outer fitting root part (or inner fitting root part) adjacent to the outer fitting crest part (or inner fitting crest part); andthe ratio obtained by divi