A portable adjustable bending device comprises a workbench composed of supports and a bench top. The bench top is provided with a fixing rod and a strip opening. A movable rod is arranged in the strip opening. The lower portion, penetrating the workbench, of the movable rod is provided with a rotating device. The rotating device comprises a vertical plate. The lower portion of the vertical plate is provided with a horizontal bottom plate. The side face of the vertical plate is provided with a structure capable of moving vertically and transversely. The upper end of a rotating rod is fixed to the lower end of the movable rod. The lower end of the rotating rod is in fit transmission with an output shaft of a servo motor through a transmission mechanism and a power mechanism. The transmission mechanism comprises a first transmission wheel, a middle gear and a driving wheel. The first transmission wheel is arranged on the rotating rod in a sleeving manner. The middle gear is meshed with the first transmission wheel and the driving wheel. The driving wheel is connected with the power mechanism through a connection shaft penetrating the bottom plate. A first connection rod and a second connection rod are arranged among the connection shaft, the rotating rod and a middle gear shaft rod. The middle gear is supported jointly through the first connection rod and the second connection rod. The portable adjustable bending device can be operated automatically and achieve precise control over the bending angles of cables.