A battery module includes first and second modules each including a series of cell stacks, each including a series of unit cells arranged in a first direction, and an insulation member insulating at least one unit cell. The battery module also includes a module housing, a coupling part on the module housing configured to couple the module housings of the first and second modules together, and a series of receiving parts in the module housing accommodating the cell stacks. Each receiving part includes a fixed wall around a respective cell stack and having at least a portion that is in contact with the respective cell stack. The coupling part includes a connector configured to electrically connect the module housings of the first and second modules together.