A battery state of charging, SOC, estimating apparatus , comprising: an input/output power pattern analyzing unit which analyzes an input/output power of a battery during a predetermined time to obtain an input/output power pattern of the battery; an application status determining unit which analyzes the input/output power pattern of the battery to determine a current application status of the battery; and an SOC calculating unit which calculates an SOC of the battery using a state of charging estimation algorithm corresponding to the current application status of the battery, characterized in that the current application status of the battery includes one or more of a constant current status, a photovoltaic status, a frequency regulation status, and a peak shaving status: - the constant current status referring to a status where a constant current flows in the battery and the battery is charged or discharged with the constant current; - the photovoltaic status referring to a status where a power is photovoltaically generated in the battery; - the frequency regulation status referring to a status where the battery is used to adjust a frequency in order to maintain the frequency when a load is changed; and - the peak shaving status refers to a status where the battery is used to supply an emergency power in order to shave a peak load during a peak time of the system; wherein a smart SOC moving estimation algorithm comprises estimating a change of an open circuit voltage based on change between a previous value and a current value of a terminal measurement voltage without using a current value, and estimating the SOC based on the estimated open circuit voltage; the SOC estimation algorithm including an extended Kalman filter SOC estimation algorithm and the smart SOC moving estimation algorithm, in that when the current application status of the battery is the constant current status or the photovoltaic status, the SOC calculating unit calculates the SOC of the battery using the extended Kalman filter SOC estimation algorithm, and in that when the current application status of the battery is the frequency regulation status or the peak shaving status, the SOC calculating unit calculates the SOC of the battery using the smart SOC moving estimation algorithm. an input/output power pattern analyzing unit which analyzes an input/output power of a battery during a predetermined time to obtain an input/output power pattern of the battery; an application status determining unit which analyzes the input/output power pattern of the battery to determine a current application status of the battery; and an SOC calculating unit which calculates an SOC of the battery using a state of charging estimation algorithm corresponding to the current application status of the battery, - the constant current status referring to a status where a constant current flows in the battery and the battery is charged or discharged with the constant current; - the photovoltaic status referring to a status where a power is photovoltaically generated in the battery; - the frequency regulation status referring to a status where the battery is used to adjust a frequency in order to maintain the frequency when a load is changed; and - the peak shaving status refers to a status where the battery is used to supply an emergency power in order to shave a peak load during a peak time of the system; <EOS>