A quaternary magnetic memory cell is of a cross-shaped structure made of a magnetic material, and comprises a horizontal magnet arm, a vertical magnet arm and a cross knot formed by crossing the magnet arm and of four magnetized states. When the horizontal magnet arm and the vertical magnet arm form up-down and left-right magnetization directions, four magnetization directions can stably exist at the cross knot and are defined as "0", "1", "2", "3" in the quaternary. When data are written in, a magnetic head changes the magnetization direction of the horizontal or vertical magnet arm, so as to change the magnetization direction at the cross knot further. When the data are read, the magnetic head reads the magnetization direction at the cross knot by electromagnetic induction.