A battery assembling body capable of preventing a temperature rise of a battery while preventing an inflow of foreign matters. The battery assembling body (12) includes a housing (15) which contains batteries (2a, 2b, 6), a side frame (17) which is used to detachably fit the housing (15) to a lower frame of a vehicle, a ventilation hole (18c) located upper part of the housing (15), and a ventilation space (24a, 24b) which is formed between the housing (15) and the batteries, and the ventilation space (24, 24b) is in communication with the ventilation hole (18c).