PURPOSE: To prevent a cell backup circuit for a memory from waste electric power consumption due to a capacitor while keeping the merits of the capacitor by providing a diode interrupting current flowing from the cell circuit to the capacitor to said circuit.

CONSTITUTION: A cell backup circuit for a memory is provided with a capacitor 5 to prevent a DC power source Vcc from voltage variation or to use it as electric power source backup unit. The capacitor 5 is connected in parallel with a cell circuit B through a diode 6. The diode 6 is connected so as to interrupt only the current flowing into the capacitor 5. Consequently electric power is always supplied from the DC power source Vcc to a memory 1 through the diodes 7, 6. When the DC power souce Vcc is cut off, the electric power of the cell 4 is supplied to the memory 1 through a diode 3. At the time of replacement of the cell 4, the energy charged on the capacitor 5 is supplied to the memory 1 through the diode 6.