A battery monitoring apparatus includes an electric power supply terminal connected with a first electrical path, a voltage input terminal connected with a second electrical path, a signal control unit connected with a third electrical path, a response signal input terminal connected with a fourth electrical path, and a calculating unit. The signal control unit is configured to cause a predetermined AC signal to be outputted from a storage battery with the storage battery itself being an electric power source for the output of the predetermined AC signal. The calculating unit is configured to calculate, based on a response signal of the storage battery to the predetermined AC signal, a complex impedance of the storage battery. Moreover, at least one of the first to the fourth electrical paths is merged with at least one of the other electrical paths into an electrical path that is connected to the storage battery.