The plug guide comprises a bore for receiving a nail comprising a head and a shaft onto which a skirt is slid, the bore having a passing section determined so that the head and the skirt of the nail cause it to be guided therein, a recess being provided in the front part of the plug guide for ejecting and expanding the guiding skirt. The recess comprises at least one radial bulge projecting inside, for extending the wall of the bore of the plug guide and forming a narrowing for guiding the nail. This invention further relates to a fastening device comprising the plug guide.