The invention discloses a steel bar bender capable of adjusting a steel bar bending radius. The steel bar bender comprises a bender body, a motor, a motor output shaft, and a central pin roll arranged on a working face of the bender body. The motor output shaft passes through the central pin roll and is connected with a rotating plate. A plurality of semi-circular rings are arranged on the bender body; the semi-circular rings and the central pin roll are concentric; and a bending track is formed between each two adjacent semi-circular rings. A clamping device is arranged inside a mounting track. An expansion device is connected between the clamping device and the rotating plate in a rotatable mode and includes two reverse threaded rods and a rotating cylinder; the two reverse threaded rods are respectively arranged at two sides inside the rotating cylinder; and threads cooperating with the reverse threaded rods are arranged at the inner wall of the rotating cylinder. According to the steel bar bender, the cost is lowered and the efficiency is improved.