POWER SUPPLY DEVICE

A failure of battery modules is reliably determined. A power supply device includes: battery modules () each of which included a failure determination unit () configured to determine a failure and a normality and to output the failure and the normality as a High signal and a low signal; a failure transmission line () connected to the failure determination unit () of each battery module (); and a module failure determination circuit () connected to the failure transmission line () and configured to determine failure and normality of the battery modules (). The module failure determination circuit () includes: a voltage determination circuit () configured to determine a High level and a Low level of the failure transmission line (); an impedance detection circuit () configured to detect an impedance with respect to a ground line (); and a calculation circuit () configured to determine the failure and the normality of the plurality of battery modules () and an abnormality of the failure transmission line () based on outputs of the voltage determination circuit () and the impedance detection circuit ().