A secondary battery system comprises a secondary battery which receives regenerative electric power from a motor, a heat storage unit (heat storage device) which converts a part of electric power stored in the secondary battery or the regenerative electric power from the motor into heat and stores the heat, and which supplies the stored heat to the secondary battery when a temperature of the secondary battery is less than a low-temperature-side threshold value which is set in advance when the electric power is extracted from the secondary battery, and an electric power distribution controller (ECU) which distributes the regenerative electric power from the motor to the secondary battery and the heat storage unit (heat storage device) when the temperature of the secondary battery is less than the low-temperature-side threshold value when the secondary battery receives the regenerative electric power from the motor.