A battery module includes a battery module, which includes a battery unit and a casing for receiving the battery unit. The casing includes a first casing body, a second casing body assembled to the first casing body, and a first sealing ring disposed between the first casing body and the second casing body. The first casing body includes a first cover plate and first sidewalls connected to edges of the first cover plate. A slot is defined on outer surface of the first sidewalls. The second casing body includes a second cover plate and second sidewalls connected to edges of the second cover plate. A latch is disposed at inner surface of the second sidewalls, corresponding to the slot. The latch is configured to be received in the slot, locating and sealing the second cover plate on the first cover plate by compressing the first sealing ring.