A voltage detection apparatus for a battery system used to supply electric power to a motor as a drive source of a hybrid electric vehicle including a first battery pack, a second battery pack and a third battery pack, wherein a plurality of unit cells made of secondary batteries are connected in series to each other in each of the first, the second and the third battery packs, the voltage detection apparatus comprising: a first circuit board that is provided on the first battery pack and that includes; a first high voltage detection portion adapted to detect a voltage of the first battery pack; a control portion adapted to control the first high voltage detection portion; and a first insulation device adapted to connect the first high voltage detection portion with the control portion; a second circuit board that is provided on the second battery pack and that includes: a second high voltage detection portion adapted to detect a voltage of the second battery pack; and a second insulation device adapted to connect the second high voltage detection portion with the control portion provided on the first circuit board; and a third circuit board that is provided on a third battery pack and that includes a third high voltage detection portion which is connected in series with the second high voltage detection portion and which is adapted to detect a voltage of the third battery pack, wherein the control portion provided on the first circuit board, which is connected in series with the second circuit board and the third circuit board, is adapted to control the second high voltage detection portion and the third high voltage detection portion through a daisy chain communication, characterized in that the second high voltage detection portion is connected via a cable to temperature sensors for detecting cell temperatures of the unit cells in the second battery pack, wherein results of a voltage detection and a temperature detection are transmitted through the daisy chain communication. a first circuit board that is provided on the first battery pack and that includes; a first high voltage detection portion adapted to detect a voltage of the first battery pack; a control portion adapted to control the first high voltage detection portion; and a first insulation device adapted to connect the first high voltage detection portion with the control portion; a second circuit board that is provided on the second battery pack and that includes: a second high voltage detection portion adapted to detect a voltage of the second battery pack; and a second insulation device adapted to connect the second high voltage detection portion with the control portion provided on the first circuit board; and a second high voltage detection portion adapted to detect a voltage of the second battery pack; and a second insulation device adapted to connect the second high voltage detection portion with the control portion provided on the first circuit board; and a third circuit board that is provided on a third battery pack and that includes a third high voltage detection portion which is connected in series with the second high voltage detection portion and which is adapted to detect a voltage of the third battery pack, wherein the control portion provided on the first circuit board, which is connected in series with the second circuit board and the third circuit board, is adapted to control the second high voltage detection portion and the third high voltage detection portion through a daisy chain communication, characterized in that the second high voltage detection portion is connected via a cable to temperature sensors for detecting cell temperatures of the unit cells in the second battery pack, wherein results of a voltage detection and a temperature detection are transmitted through the daisy chain communication.