The invention relates to a positioning device for in-situ windowing of an endovascular stent-graft. The positioning device comprises a push piece, a conveying sheath and a guiding wire, wherein a first through hole is formed in the push piece, a first magnetic piece is arranged at the first end of the push piece, and a guiding wire hole communicated with the first through hole is formed in the first magnetic piece; a second through hole is formed in the conveying sheath, a second magnetic piece is arranged at the first end of the conveying sheath, a third through hole communicated with the second through hole is formed in the second magnetic piece, and the first magnetic piece is connected with the second magnetic piece in a magnetic attracting manner; and the guiding wire is used for conveying the first magnetic piece and the second magnetic piece. The positioning device provided by the invention has the benefits as follows: after folding of the magnetic pieces, windowing is achieved through guided laser burning punching or a puncture needle method, the step of windowing is simplified, operating difficulty and risks are lowered, the operation time is saved, equipment customization is avoided, and moreover, the operation cost is lowered.