Abstract: An adjustable wrench has a handle and a head formed integrally at the anterior end of the handle. The head is provided with a fitting hole, a receiving hole, and a through hole in communication with the fitting hole. Located at two opposite sides of the fitting hole are two fixed clamping surfaces. A rotation knob is disposed in the receiving hole. An adjustment bolt is put through the through hole and the ring hole of the rotation knob such that one end of the adjustment bolt is received in the fitting hole. The one end of the adjustment bolt is provided with a movable clamping surface forming a clamping space in conjunction with the two fixed clamping surfaces. The ring hole of the rotation knob is provided with threads engageable with threads of the adjustment bolt. A location pin is fastened to the head such that the locating pin is inserted into a groove extending axially in the adjustment bolt.