A lightweight eddy current rail brake 11 to be mounted on a bogie frame of a railway car comprises a magnet unit 12 which generates an electromagnetic attraction force with respect to a rail 5 and which comprises an elongated support member 15 and a plurality of permanent magnets 17. The support member 15 is ferromagnetic and extends generally parallel to the direction in which a side beam of a bogie frame extends, and it is rotatable about a shaft which is generally parallel to this direction. A plurality of permanent magnets 17 are arranged on the support member 15 in series and are spaced above a rail 5. At least two adjoining permanent magnets 17 of the plurality of permanent magnets 17 are arranged so as to have different polarities from each other.
