A battery pack includes a secondary battery, a state of charge calculator, an integrated current amount calculator, a differential state of charge calculator, a full charge capacity calculator, and a charging-and-discharging control section. The differential state of charge calculator calculates a differential state of charge between a first state of charge at a first detection timing and a second state of charge at a second detection timing. The integrated current amount calculator calculates an integrated amount of a current flowing to the secondary battery in a subject period from the first detection timing to the second detection timing. The full charge capacity calculator calculates a full charge capacity of the secondary battery based on the differential state of charge and the integrated current amount. The charging-and-discharging control section is configured to restrict one of the charging and the discharging of the secondary battery during the subject period.