A threaded joint for oil well steel pipe is provided. The threaded joint includes a pin provided with a male thread, and a box provided with a female thread threadedly engaged with the male thread, and at an outer periphery side sealing portion, a cross-sectional area S1 of the pin at a seal point, and a cross-sectional area S0 of a pipe body portion, which is an unprocessed pin portion, satisfy an expression (S1/S0)×100≥15(%), at an inner periphery side sealing portion, a cross-sectional area S2 of the box at a seal point, and a cross-sectional area S0′ of a pipe body portion, which is an unprocessed box portion satisfy an expression (S2/S0′)×100≥20(%), and a surface area S3 of a contact portion of an intermediate shoulder between thread rows and the cross-sectional area S0 satisfy the expression (S3/S0)×100≥10(%).