To provide a fastening tool easily and efficiently performing fastening work of a bolt and a nut of a screw fastening body of a pipe joint in a short period of time.

The fastening tool is equipped with: a body 2; a first socket mounting part 4 provided on the body 2; a fastening screw 8 provided at a position opposed to the first socket mounting part 4 of the body 2 and advanceable/retreatable in a direction of the first socket mounting part 4; a second socket mounting part 12 provided on a distal end of the fastening screw 8; a first socket 15 detachably mounted to the first socket mounting part 4 and capable of fitting any one of a head part of the bolt 31 of the screw fastening body 30 or the nut 33; and a second socket 18 detachably mounted to the second socket mounting part 12 and capable of fitting the other one of the head part of the bolt 31 of the screw fastening body 30 or the nut 33.