To correctly measure a cell residual capacity stored therein by removing the usage state of a secondary cell and the influence of a circumferential environment.

When a voltage value detected by a voltage sensor 34 is a prescribed value or more, a current value detected by a current sensor 32 is a prescribed value or less, and a temperature detected by a temperature sensor 33 is a normal temperature or more in a charge process of a device for measuring the residual capacity of a cell, the full charging amount of a lithium-ion battery 31 stored in a memory 8 is replaced by the residual capacity calculated by a calculating unit 1. In a stop process, as well as the charging process, after the temperature is checked, the full charging amount is corrected. The direction of the current flowing in the lithium-ion battery 31 before stopped is stored in a memory 81. An open circuit voltage (after charged)-residual capacity rate memory table 61 and an open circuit voltage (after discharged)-residual capacity rate memory table 62 are used according to the direction of the current immediately before stopped.

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