PURPOSE: To easily perform the magnetic separation of a slurry by providing an exteinal magnetic field apparatus becoming polarity different from that of the internal magnetic field apparatus in an induction magnetic drum to the outside of the bottom part of a non-magnetic tank and radially arranging ferromagnetic matrices to the entire peripheral surface of the drum.

CONSTITUTION: Both ends of the center shaft of an induction magnetic drum are supported by bearings 6 so as to be made freely rotable by a drive motor 12 and ferromagnetic matrices 5 are radially arranged to the entire peripheral surface of the drum 3 so as to form an angle θ with respect to the line passing through the center of the drum 3. The drum 3 having an internal magnetic field apparatus 1 therein as a fixed pole is received in a non-magnetic tank 9 having an ore supply port I, a concentrate discharge port Po, a magnetic matter discharge port Mo and a washing nozzle 11 and external magnetic field apparatuses 2A, 2B having polarity different from that of the internal magnetic field apparatus 1 in the drum 3 are arranged to the outside of the bottom part of the tank 9 to constitute a pair of magnetic field apparatuses. The positional relation between the drum 3, the motor 12, the tank 9 and the apparatuses 2A, 2B is held by a frame 10.