Provided is a magnetic filter device for preventing the reduction in magnetic field strength at positions at a distance from the magnet unit. The magnetic filter device (1A, 1B) is provided with: a processing vessel (6) having a processing chamber (S1) for adsorbing ferromagnetic particles dispersed in the fluid being processed that is flowing therein using magnetic force to filter and remove same from the fluid being processed; a magnet unit (2) in which multiple magnetic poles comprising different magnetic poles are disposed along the direction of flow of the fluid being processed and which is configured so as to be located outside the processing chamber (S1); and one or more magnetic yokes (41), which are provided inside the processing chamber (S1) so as to allow flow of the fluid being processed and which draw magnetic force lines respectively originating in the multiple magnetic poles in directions away from the magnet unit (2) inside the processing chamber (S1).