Network device with uninterruptible power supply function

A network device with an uninterruptible power supply function is provided. The network device includes a network physical transmission unit, a power connecting part and a backup power supply module. The network physical transmission unit is operated at a user terminal according to a fiber to the home (FTTH) technology or a fiber to the building (FTTB) technology. The power connecting part is in communication with an external power source for receiving electricity from the external power source to operate the network device. If the electricity transmitted from the external power source to the network device is interrupted, the backup power supply provides backup electricity to the network device to maintain normal operation of the network device.