An apparatus for converting terminal polarity for RS communication includes a comparator configured to discriminate polarities of a first signal line and a second signal line by comparing voltage levels indicated on the first and second signal lines of a cable for RS-485 communication, a switch unit configured to connect a TRXD+ terminal to the first signal line and connect a TRXD− terminal to the second signal line, or to connect a TRXD+ terminal to the second signal line or connect a TRXD− terminal to the first signal line in response to a provided switch control signal, and a switch controller configured to transmit the switch control signal to the switch unit in response to a polarity discrimination result by the comparator relative to the first signal line and the second signal line.