BATTERY PACK

A battery pack includes a main circuit board 40, and a plate-shaped heat-dissipating block 42. The circuit board 40 is connected to batteries 11 of a battery unit 10. The block 42 is thermally connected to a heat-generating component 41. An exterior case 30 includes two opposed surface plates 33 and side walls that close peripheral parts of the plate 33, and has a box shape the width of which is larger than the thickness. The block 42 is spaced away from the unit 10 in the case 30, and does not overlap the unit 10. The block 42 is arranged in parallel to the plate 33 in the case 30. A surface of the block 42 opposed to the plate 33 is thermally connected to the plate 33. Heat from the component 41 can be conducted to the block 42. The heat can be dissipated from the plate 33.