A PLC maintenance support device according to the present invention includes a signal identification tag reader for reading a signal address from a signal identification tag attached to an input and output signal cable of a PLC to identify the signal address of the input and output signal cable, a transmitter for transmitting the signal address identified by the signal identification tag reader to the PLC, a receiver for receiving the on or off state of a signal corresponding to the transmitted signal address from the PLC, and a monitor for displaying the received on or off state of the signal.
