<p>Disclosed is a pipe screw coupling that has increased sealing properties, compression resistance, and galling resistance. Specifically, the pin nose outer peripheral surface (30) forms a convex curve on the outside thereof in a cross section in the axial direction. Said convex curve has a curved shape wherein a compound-R curve (N) comprising a plurality of outwardly convex arcs that are connected in sequence and that have radii of curvature (R) that differ from each other at the generating line of a cylindrical section that is adjacent to a male screw section (5) is such that the radii of curvature (R) of the arcs increase with distance from the male screw section (5) and the line tangent to the connection point of an arc is the same as that of the arc connected to. The inner peripheral surface relative to the pin nose (30) of a box member (1) has a tapered surface (20) that interferes with the pin nose outer peripheral surface (30) when connecting with the pin member (3).</p>
