A battery monitoring device includes a control unit; electric elements respectively connected in parallel to battery cells; main analog-digital converters that are respectively connected to the battery cells via the electric elements, and respectively detect voltages of the battery cells; and sub analog-digital converters that are respectively connected to the battery cells without using the electric elements, and respectively detect the voltages of the battery cells. The control unit is configured to determine whether there is a failure in each electric element based on a first voltage detection value detected by the main analog-digital converter, and a second voltage detection value detected by the sub analog-digital converter. The control unit is configured to limit a control range of a degree of charge as compared to that used during a normal control, when it is determined that there is a leak failure in at least one of the electric elements.