A battery pack is provided which includes a battery, a circuit board equipped with load feed lines, bus bars connecting with the battery and the circuit board, first and second switches, and third to sixth switches. The first and second switches are disposed in a housing which is higher in capacity of heat dissipation than the circuit board. The third to sixth switches are disposed on the circuit board. The first and second switches are larger in amount of electrical current flowing therethrough than the third to sixth switches on time average. This enables the size of the battery pack to be reduced without sacrificing the dissipation of heat from the switches.