The invention discloses a positioning device for punching an inclined hole in a thin-wall irregular-shaped structural part. The positioning device comprises a shell which is hollow, the side wall of one side of the shell is provided with a feed inlet which communicates with the interior of the shell, a cover plate is rotationally connected to an opening of the feed inlet, a punching mechanism is connected to the inner wall of the upper side of the shell through a lifting mechanism, an installation plate is arranged in the shell, a sliding rod and a thread rod are transversely arranged in the shell in parallel and close to the lower end of the shell, the sliding rod penetrates through the installation plate and is in sliding connection with the installation plate, and the thread rod penetrates through the installation plate and is in threaded connection with the installation plate. Operation is convenient, the position of the thin-wall irregular-shaped structural part can be adjusted, the thin-wall irregular-shaped structural part does not need to be taken down and fixed again, the device application range is enlarged, the labor intensity of workers is greatly reduced, time is saved, and working efficiency is improved.