Even if a network setting changes due to power interruption or the like, communication for controlling the operating status of load devices of an uninterruptible power supply is enabled to continue. A network communication system (1) for the uninterruptible power supply comprises UPS member controllers (12 and 13) and a UPS group controller (11) which are connected in a network (2) to control the operating status of the load devices (3) of the uninterruptible power supply (1). The UPS group controller (11) and the UPS member controllers (12 and 13) execute data communication according to a predetermined communication protocol (Internet Protocol or the like) through the network (2), and these controllers transmit/receive data in which specific identification information issued for each of the UPS member controllers (12 and 13) is added to control data as communication data in the data communication according to the predetermined communication protocol.