A data erasing device that erases data recorded on a magnetic disk, by a magnetic field generated in a horizontal direction by magnets, in order to prevent leakage of the data recorded on the magnetic disk of a magnetic disk device to be abandoned. The data erasing device includes a main body case having a path on which a tray is reciprocated, a demagnetizing circuit having plural permanent magnets adjacently disposed along the path in mutually adsorbing polarities, and a tray for accommodating the magnetic recording medium, and capable of reciprocating on the path. This tray includes a first accommodation groove and a second accommodation groove for accommodating the magnetic disk device. The first accommodation groove and the second accommodation groove cross each other to form an angle of 45 degrees or 90 degrees.