A battery monitoring device for monitoring a cell group made by connecting a plurality of single battery cells in series includes a reference voltage generation circuit configured to generate a variable reference voltage, a switching circuit configured to select, as a measurement target voltage, any one of a plurality of types of voltages including the cell voltages of the single battery cells in the cell group and the reference voltage, and an AD converter configured to measure the measurement target voltage which is selected by the switching circuit, and output a digital signal according to the measurement result.