A battery unit has battery cells having electrode terminals, bus bars having voltage potential detection terminals, a control board having a voltage detection circuit and a discharge duct. In the battery cell, the electrode terminals of the battery cells are electrically connected to the voltage potential detection terminals of the bus bars. The voltage potential detection terminals of the bus bars are electrically connected to the voltage detection circuit formed on the control board through metal conductive members or lines. The voltage detection circuit detects a voltage potential of each of the battery cells through the metal conductive members. The metal conductive members are not dedicated components, and integrated with the discharge duct by insert molding.