The invention discloses a ferromagnetic substance filter device, comprising a fixing frame, wherein a driving winding drum, a first driven winding drum, a second driven winding drum and a third driven winding drum, which are horizontally arranged are arranged at four corners of the fixing frame respectively; one end of the driving winding drum is connected with a motor through a speed reducer; a plurality of annular grooves are arranged in the bodies of the driving winding drum, the first driven winding drum, the second driven winding drum and the third driven winding drum at intervals; a plurality of annular magnetic chains are correspondingly embedded into the annular grooves corresponding to the driving winding drum, the first driven winding drum, the second driven winding drum and the third driven winding drum; and the annular magnetic chains are formed by a plurality of magnetic rods connected through hinges, so as to form a magnetic curtain of adsorbing ferric particles. The ferromagnetic substance filter device has good functions of adsorbing and removing the ferric particles, can effectively reduce the mass defect of follow-up work and reduce the product grade, and can be widely applied to the field of reuse treatment of emulsified liquid of a rolling mill.