A battery module includes a first heat transfer component and a first thermal expansion material member that are disposed between the battery cells adjacent to each other. The first thermal expansion material member has a thermal conductivity lower than a thermal conductivity of the first heat transfer component and expands at a first predetermined temperature or higher, in which when temperature of the first thermal expansion material member is less than the first predetermined temperature, the adjacent battery cells are connected to each other via a high thermal conductive route including the first heat transfer component and having a first thermal conductivity, and in which when the temperature of the first thermal expansion material member reaches the first predetermined temperature or higher, the adjacent battery cells are connected to each other via a low thermal conductive route having a second thermal conductivity lower than the first thermal conductivity.