Abstract: A method for estimating a state of health (SOH) of a battery includes obtaining a state of charge (SOC)-open circuit voltage (OCV) lookup table according to a SOH of a battery module or battery pack, and storing the SOC-OCV lookup table in a memory, calculating, based on a diagnosis time and a current rate, a first SOC change amount when the diagnosis time and the current rate are input, calculating a first slope for each SOC section corresponding to the first SOC change amount according to the SOH in the SOC-OCV lookup table according to the SOH, and determining, based on the first slope, first sections having high diagnostic accuracy.