Switch failure diagnosis device and electric storage apparatus

A switch failure diagnosis device for using in a current path between an electric device and an electric storage device, the switch failure diagnosis device comprising:

• a plurality of switches connected parallel to each other in the current path between the electric device and the electric storage device;
• a switch terminal voltage detector configured to output a switch terminal voltage detection signal corresponding to a voltage across the switches;
• and
• a controller configured to:
• select the switches at different time in sequence and input an open instruction signal to each switch at the time when the switch is selected;
• and
• determine, based on the switch terminal voltage detection signal output while the open instruction signal is given, that at least one of the switches has a failure if the detected voltage is in a failure determination range.