A rotor component and an external rotor motor comprising the rotor component, a plurality of magnetic pieces, an axle, and a magnetic ring. The rotor component includes a plate and a tubular outer shell extending from the edge of the plate. The tubular outer shell forms an annular cavity in the middle and is fitted to the outer surface of the magnetic ring. The characteristic is that the rotor shell and the magnetic ring are cast integrally. The inner wall of the tubular outer shell has an upper step and a lower step. The two end faces of the magnetic ring are respectively supported on the upper step and the lower step. A plurality of magnetic pieces are mounted on the inner wall surface of the magnetic ring in circumferential intervals. The rotor shell is made of cast aluminum