The magnetic data eraser includes: a mounting and immobilizing tray on which a magnetic recording medium is mounted, the mounting tray being inclined at an angle of 60±10 degrees to the horizontal; a magnetizer that is encircled by a magnetizing coil, the magnetizer having a hollow portion into which the mounting and immobilizing tray is inserted; and a controller that causes an electric current to flow as an excitation current through the magnetizing coil, the excitation current generating a magnetic field that erases data stored in the magnetic recording medium.