An apparatus and a method are provided for monitoring a battery pack for accurately calculating an actual discharging or charging capacity of a secondary battery, which depends on temperature. The battery pack monitoring apparatus includes a bare cell adapted to be charged/discharged with a predetermined voltage. Sensors sense the bare cell charging/discharging voltages, charging/discharging currents, and temperature and convert them into predetermined electrical signals. A monitoring control unit converts the electrical signals from the sensors into digital signals and processes them in accordance with predetermined control commands. A storage unit stores tabulated discharging capacity-time data and charging capacity-time data as a function of the bare cell temperature, and outputs this data to the monitoring control unit. The processed data indicating a current charge/discharge capacity of the battery pack is provided to a charger or to another external system.