The invention discloses a Cu-Nb composite wire straightening device which comprises a rack. A paying-off wheel, a first straightening unit, a second straightening unit, a guide wheel and a trailer wagon are installed on the rack in sequence. The paying-off wheel is rotationally installed at the upper end of a paying-off spool shaft. The lower end of the paying-off spool shaft is fixed to the rack. A tension device is fixed to the paying-off spool shaft, wherein the end of the tension device makes contact with the lower end face of the paying-off wheel, and the tension device prevents a Cu-Nb composite wire from being disengaged. The first straightening unit and the second straightening unit are of the same structure. The first straightening unit is horizontally installed, the second straightening unit is vertically installed, the guide wheel is installed at the upper end of a supporting rod, the lower end of the supporting rod is fixed to the rack, a driving device used for driving the trailer wagon to walk is installed on the rack, the rack is provided with a discharging groove and a walking rail used for enabling the trailer wagon to walk, and the discharging groove is located below the walking rail. The Cu-Nb composite wire straightening device can be well applicable to Cu-Nb composite wire straightening, is good in straightening effect, facilitates replacement of straightening components, and is low in using cost.