PURPOSE: To provide a memory backup circuit which prevents the breakdown due to the charging of a lithium battery used for the backup circuit of a memory such as a RAM or the like.

CONSTITUTION: In a memory backup circuit by which a RAM 1 installed at a computer is backed up by a lithium battery 6, a contact (b) 11b for a relay which is operated only when a power supply 2 for a computer body is turned on is interposed and installed in series with a backup power-supply line 7 across the lithium battery 6 and the RAM 1.