PURPOSE: To accurately confirm the remaining service life of a battery by providing a means which charges and discharges the battery, means which measures the time required to discharge the battery, and means which displays the measured results of the measuring means.

CONSTITUTION: When a control circuit 1 repeats discharging and charging of a battery 7 a plurality of times, a charge circuit 2 starts the charging upon receiving a charge starting signal from the circuit 1 and, upon completing the charging signal to the circuit 3. A discharge circuit 3, on the other hand, starts the discharging upon receiving a discharge starting signal from the circuit 1 and, upon completing the discharging, outputs a discharge completing signal to the circuit 1. A discharging time measuring circuit 4 starts measurement upon receiving a measurement starting signal from the circuit 1 at the time of starting, for example, the third discharging operations, stops the measurement upon receiving a discharge completing signal from the circuit 3, and outputs the measured time, namely, the time required for discharging the battery 7 to a display circuit 5. The circuit 5 displays the measured results of the circuit 4.