The invention discloses a cable straightening device. The cable straightening device comprises a workbench, a conveying mechanism, a positioning mechanism and a straightening mechanism; the conveying mechanism comprises conveying plates, conveying bases, conveying belts and lifting plates, wherein adjusting wheels are arranged on the lifting plates, and a plurality of cable grooves are uniformly formed in the conveying plates in the width direction of the conveying plates; the positioning mechanism comprises a mounting frame, a rectangular positioning frame and a cross beam, wherein the cross beam is provided with positioning arms, the rectangular positioning frame is connected to the positioning arms through a positioning assembly, the positioning assembly comprises a lifting positioning plate, and positioning grooves are formed in the bottom of the rectangular positioning frame; and the straightening mechanism comprises a sliding base, a straightening air cylinder and a straightening plate, wherein straightening grooves matched with the cable grooves are formed in the straightening plate in the width direction of the straightening plate, and rolling wheels are further embedded in the straightening plate. The cable straightening device has the advantages that the structure is compact, use is convenient, the labor intensity of workers can be greatly reduced, and the straightening efficiency and the straightening quality of a cable can be effectively ensured.