A device of estimating a state-of-health of a battery, the device comprising: a memory configured to load a program for calculating a state-of-balance value by voltage of a plurality of cells constituting the battery and estimating a state-of-health balance value which is a state-of-health value of the battery to which the state-of-balance value by voltage is applied; and a processor configured to execute instructions included in the program loaded by the memory; wherein according to executing of the program, the processor is configured to: set a voltage difference allowable limit value within a voltage difference between a fully charged-state voltage and a discharged-state voltage of the battery, set an allowable limit quantile which subclassifies, into one or more analysis sections, an allowable limit range to which the voltage difference allowable limit value is applied with respect to an average voltage value derived from measured voltage values of the cells, calculate a voltage drop rate in the allowable limit range with respect to the average voltage value, wherein a quantile drop rate based on the allowable limit quantile is calcualted as the voltage drop rate, derive a quantile degree, which is a degree of the analysis section in which the measured voltage values for each cell are all included within the allowable limit quantile for a first time, calculate the state-of-balance value by voltage based on the quantile drop rate and the quantile degree, and estimate the state-of-health balance value by applying the state-of-balance value by voltage to the state-of-health value calculated based on a remaining capacity of the battery. a memory configured to load a program for calculating a state-of-balance value by voltage of a plurality of cells constituting the battery and estimating a state-of-health balance value which is a state-of-health value of the battery to which the state-of-balance value by voltage is applied; and a processor configured to execute instructions included in the program loaded by the memory; wherein according to executing of the program, the processor is configured to: set a voltage difference allowable limit value within a voltage difference between a fully charged-state voltage and a discharged-state voltage of the battery, set an allowable limit quantile which subclassifies, into one or more analysis sections, an allowable limit range to which the voltage difference allowable limit value is applied with respect to an average voltage value derived from measured voltage values of the cells, calculate a voltage drop rate in the allowable limit range with respect to the average voltage value, wherein a quantile drop rate based on the allowable limit quantile is calcualted as the voltage drop rate, derive a quantile degree, which is a degree of the analysis section in which the measured voltage values for each cell are all included within the allowable limit quantile for a first time, calculate the state-of-balance value by voltage based on the quantile drop rate and the quantile degree, and estimate the state-of-health balance value by applying the state-of-balance value by voltage to the state-of-health value calculated based on a remaining capacity of the battery. set a voltage difference allowable limit value within a voltage difference between a fully charged-state voltage and a discharged-state voltage of the battery, set an allowable limit quantile which subclassifies, into one or more analysis sections, an allowable limit range to which the voltage difference allowable limit value is applied with respect to an average voltage value derived from measured voltage values of the cells, calculate a voltage drop rate in the allowable limit range with respect to the average voltage value, wherein a quantile drop rate based on the allowable limit quantile is calcualted as the voltage drop rate, derive a quantile degree, which is a degree of the analysis section in which the measured voltage values for each cell are all included within the allowable limit quantile for a first time, calculate the state-of-balance value by voltage based on the quantile drop rate and the quantile degree, and estimate the state-of-health balance value by applying the state-of-balance value by voltage to the state-of-health value calculated based on a remaining capacity of the battery.