A threaded joint for oil country tubular goods comprising: pins each of which occupies a pipe end portion of a steel pipe for an oil country tubular goods, and includes an externally-threaded portion, a nose portion which extends toward a pipe end side from the externally-threaded portion, and a shoulder portion forming a distal end of the nose portion; and a box which includes internally-threaded portions each forming a threaded portion by being threadedly joined with the externally-threaded portion, and shoulder portions which are brought into contact with the shoulder portions of the pins, the pins and the box being joined to each other by the threaded joining so that portions between the threaded portions (5, 7) and the shoulder portions (12, 14) are brought into metal-to-metal contact with each other thus forming seal portions (11, 13) at the contact portions, and the shoulder portions of the pins and the shoulder portions of the box forming shoulder faces which are brought into contact with each other at the time of fastening the threaded joint, characterized in that a pitch change is made such that an internally-threaded pitch has the same value as a externally-threaded pitch from a thread end portion on a box end side to a pitch change position, and the internally-threaded pitch is changed to a value less than the externally-threaded pitch at the pitch change position so that a thread gap is gradually decreased from the pitch change position to a position of the thread end portion on the box center side, and the thread gap is eventually set to a value which is 0.2 to 0.8 times as large as the thread gap before the pitch change is made, where the distance between the pitch change position and the end of the internally-threaded portion on a box center side is less than 1/2 of the entire length of the threaded portion, where the definition of the thread gap is as follows: The thread gap is a distance in a pipe axis direction between stabbing flank faces (31P, 31B) which face each other within a range of the threaded portions of the pin and the box in a state where load flank faces (30P, 30B) which face each other on a box end side from the pitch change position contact with each other with no gap therebetween. pins each of which occupies a pipe end portion of a steel pipe for an oil country tubular goods, and includes an externally-threaded portion, a nose portion which extends toward a pipe end side from the externally-threaded portion, and a shoulder portion forming a distal end of the nose portion; and a box which includes internally-threaded portions each forming a threaded portion by being threadedly joined with the externally-threaded portion, and shoulder portions which are brought into contact with the shoulder portions of the pins, the pins and the box being joined to each other by the threaded joining so that portions between the threaded portions (5, 7) and the shoulder portions (12, 14) are brought into metal-to-metal contact with each other thus forming seal portions (11, 13) at the contact portions, and the shoulder portions of the pins and the shoulder portions of the box forming shoulder faces which are brought into contact with each other at the time of fastening the threaded joint, characterized in that a pitch change is made such that an internally-threaded pitch has the same value as a externally-threaded pitch from a thread end portion on a box end side to a pitch change position, and the internally-threaded pitch is changed to a value less than the externally-threaded pitch at the pitch change position so that a thread gap is gradually decreased from the pitch change position to a position of the thread end portion on the box center side, and the thread gap is eventually set to a value which is 0.2 to 0.8 times as large as the thread gap before the pitch change is made, where the distance between the pitch change position and the end of the internally-threaded portion on a box center side is less than 1/2 of the entire length of the threaded portion, where the definition of the thread gap is as follows: The thread gap is a distance in a pipe axis direction between stabbing flank faces (31P, 31B) which face each other within a range of the threaded portions of the pin and the box in a state where load flank faces (30P, 30B) which face each other on a box end side from the pitch change position contact with each other with no gap therebetween.