An object of the invention is to render replacement of controllers for identifying failure information unnecessary. Failure monitor units 24 and 26 in power supplies 10 and 12 are connected mutually via paths 38 and 40, the failure monitor units 24 and 26 in the power supplies 10 and 12 are connected to failure monitor units 30 and 32 in controllers 14 and 16 via paths 34 and 36, and LEDs 1 and 2 are connected to paths 34 and 36. The failure monitor unit 24 transfers, when a failure occurs in the power supply 10, failure information to the failure monitor unit 26 in the power supply 12 via the path 38. The LED 1 is lit by both the failure monitor units 24 and 26. The failure monitor units 24 and 26 transfer failure information indicating failure occurrence in the power supply 10 to the failure monitor units 30 and 32 in controllers 14 and 16 via a path 34. The failure monitor units 30 and 32 notify a maintenance PC of the failure occurrence in the power supply 10.