A battery pack includes a first battery case accommodating a plurality of cells, and a second battery case laminated above the first battery case and accommodating a plurality of cells. The first battery case has a first through-hole on an upper surface. The second battery case has a second through-hole on a bottom surface which communicates with the first through-hole. The battery pack includes a communication port composed of the first through-hole and the second through-hole, a gas discharge valve which is provided only in either the first battery case or the second battery case and opens when internal pressure of the battery pack is higher than a predetermined value, and a temperature sensor provided on a gas flow path connected to the gas discharge valve.