Provided is a joint structure for a steel pipe pile that coaxially connects a first steel pipe pile and a second steel pipe pile and wherein: an outer fitting valley section is formed so that the plate thickness thereof increases the closer an outer fitting stepped section is to the first steel pipe pile; an inner fitting valley section is formed so that the plate thickness thereof increases the closer an inner fitting stepped section is to the second steel pipe pile; and, in a state in which an inner fitting end section is inserted in an outer fitting end section, rotated relative to the outer fitting end section, and fitted thereto, an inner fitting tip surface and the surface that faces this inner fitting tip surface are separated by a predetermined distance (D) and the overall surface area of a tension-side contact surface that is made to bear tensile force is equal to or less than the total surface area of the surface area of the outer fitting tip surface that bears compressive force and the overall surface area of a compression-side contact surface that bears compressive force.
