A threaded joint in which the outer peripheral face of the pin nose has a single tapered shape, the seal face of the box has an outwardly convex curved shape, and a seal point xp defined by equation (1) is greater than or equal to 0.2 inches, x p = ∫ x 1 x 2 ⁢ p ⁢ ⁢ x ⁢ ⁢ d ⁢ ⁢ x F ⁢ ⁢ F = ∫ x 1 x 2 ⁢ p ⁢ ⁢ d ⁢ ⁢ x ( 1 ) where p is a contact face pressure, x is a distance from an end of the pin in a pipe axis direction, and x1 and x2 are respectively a lower limit and an upper limit of a domain of x corresponding to the seal portion.