A rotation preventing structure of a terminal bus bar of a battery connector includes a battery pack that includes a pack case in which a battery assembly having arranged batteries is accommodated, a battery connector that is mounted to the battery pack, a terminal bus bar that is formed on the battery connector and has a configuration where an external connection bus bar is fastened to a bolt fixed to one end portion of the terminal bus bar and an electrode of the battery at one end of the arranged batteries is fastened to the other end portion of the terminal bus bar, opposing wall parts that are formed on a case of the battery connector and hold the terminal bus bar, and a pair of support projections that is formed on an end plate of the pack case and holds the opposing wall parts.