Patent ID: 7942216

Claim:
A drill rod comprising a fitting portion which protrudes toward a distal end of the drill rod and extends along a first axial line, wherein the fitting portion includes: a parallel male thread portion in which a minimum distance from the first axial line in a cross-section perpendicular to the first axial line is constant; and a male thread ending portion which is continuous with a proximal end of the parallel male thread portion, and in which the minimum distance increases approaching a proximal end thereof; the fitting portion is formed such that the minimum distance does not decrease approaching a proximal end from a distal end thereof; the proximal end of the male thread ending portion is positioned on a face where a distance from the first axial line gradually increases approaching the proximal end of the male thread ending portion from the parallel male thread portion; and a radius of curvature of a thread groove portion in the male thread ending portion, in a cross-section including the first axial line, is larger than a radius of curvature of a thread groove portion of a male thread formed in the parallel male thread portion, in a cross-section including the first axial line.