A device for estimating state of charge of battery of the present disclosure includes: a sensing unit configured to measure at least one of a first voltage and an OCV of a battery; and a processor operably coupled to the sensing unit. The processor is configured to estimate a second voltage of the battery based on the OCV of the battery or a previously estimated first SOC, calculate a counted voltage error by counting a voltage error between the first voltage and the second voltage of the battery, correct the second voltage of the battery depending on whether the counted voltage error is included in a reference error range, and estimate a first SOC of the battery based on the second voltage or the corrected second voltage.