BATTERY PACK

A battery pack () includes an outer case (), which comprises an upper-part case () and a lower-part case () fixed to the upper-part case (), and a cell case (), which is housed in the outer case (). An engaging part () is provided on one of the upper-part case () and the cell case (). An engaged part (), with which the engaging part () engages, is provided on or in the other of the upper-part case () and the cell case ().