PURPOSE: To enhance storage density by making a voltage level store in an element ternary or above on a storage device storing information with high density.

CONSTITUTION: Binary data is converted into the analogue voltage of a 2n value at every (n) bit by a decoder 1 and outputted. Then respective analogue voltage inputs are stored in a storage element 2 as the different magnetization state of the 2n value. Then the output voltage of the 2n value read corresponding to the different magnetization state are discriminated respectively by a decoder 3 and outputted as the binary data of (n) bit.