In order that the output voltage of a battery pack can be switched and the battery pack can be shared among different voltage electric appliances, this battery pack has a switching mechanism that switches outputting a low voltage by parallel connection of two cell units or outputting a high voltage by series connection of the two cell units, said two cell units each being composed of a plurality of cells connected in series, wherein the switching mechanism is configured from a change-over switch having an operation lever (452). The change-over switch is embedded in a battery pack (400), and an operator is able to manually switch outputting 18 V by setting the operation lever (452) at a first position or outputting 36 V by setting the operation lever (452) at a second position.