A failure determination device for a cell voltage monitor is provided. The cell voltage monitor detects cell voltages of a plurality of single cells. The failure determination device includes a minimum value determination unit for determining whether or not a present cell voltage which the cell voltage monitor detects is equal to or lower than a minimum detectable cell voltage, and a failure determination unit for determining that the cell voltage monitor has a failure. A failure is detected when the present cell voltage is equal to or lower than the minimum value cell voltage, and a cell voltage detected by the cell voltage monitor in the past and stored in the memory is greater than a determination cell voltage.