Provided is a threaded joint for an oil well tubing which possesses sufficient sealability when the external pressure is applied to the threaded joint by suppressing the plastic deformation of a nose portion and sufficient galling resistance. The sufficient galling resistance is provided by preventing the occurrence of galling at the time of making up the threaded joint during verification test performed in accordance with ISO13679:2002 even when the threaded joint for an oil well tubing has a small thickness. Parameters including sizes of the threaded joint at positions of a seal point and shoulder portions satisfy formula 1 ((Ds12−Ds02)/(D12−D02)≥0.30), formula 2 (tan θ>(ΔD+δ)/{2(Lt−Ls)}), and Ls/Ln is set to 0.2 to 0.6.