Abstract: A magnetic bulk eraser for erasing a cassette magnetic recording tape. A pair of parallel magnetic disks have alternating magnetic poles around their peripheral surface. The disks are mounted facing each other, and are so aligned that the facing poles are similar, e.g. North faces North, and South faces South. A guide slot through which a cassette magnetic tape may be passed is provided between the magnet disks. A holder having a cassette magnetic tape to be erased moves linearly through the guide slot engaging a rack with pinions. When a handle is rotated manually, the magnetic disks rotate and provide an alternating magnetic flux in the guide slot through which a cassette magnetic tape passes, also driven by the manually operated handle.