A power supply device includes: an assembled battery that is configured of N pieces of battery cells connected in series; (N+1) pieces of measurement lines that obtain analog signals corresponding to terminal potentials of the battery cells; a filter circuit that attenuates a specified frequency component of the inputted analog signals and outputs; and an analog/digital converter that converts the analog signals outputted from the filter circuit into digital signals. The filter circuit is configured of: (N+1) pieces of input terminals; (N+1) pieces of output terminals; (N+1) pieces of filter resistors; and (N+1) pieces of filter capacitors of which one ends respectively connected between the filter resistors and the output terminals and the other ends are connected to each other in common.