A switch failure detector, configured to be installed in an electric system including an electric storage device, includes at least one electronic switch connected in a path in which a charging current to the electric storage device and a discharging current from the electric storage device flow, at least one rectifier for passing a discharging current by bypassing the electronic switch when the electronic switch is turned off, and a controller for sending an on-command signal to the at least one electronic switch to turn on the electronic switch, and determining whether a switch failure detection process is executable based on a voltage of the electric storage device.