A fixing structure of a radial lead of a rotating electrical machine connects slip rings provided to a rotation shaft of a rotor and axial leads disposed in a center hole of the rotation shaft and supplying a current to a rotor coil. A radial lead is inserted into a radial lead hole penetrating through the rotation shaft in a radial direction from the center hole and a tapered male screw formed at one end is threaded into a tapered female screw formed in the axial lead while the other end is electrically connected to the slip ring. A sealing member installed to a step portion of the radial lead hole is fastened, via a spacer, by a fastening nut threaded into a straight screw of the radial lead, so that a side of the center hole is maintained airtight from an outside.