Abstract: A parameter setting method for a PLC communication system. In a transmission mode, a self-station identification number is set, and transmitting data is divided into a plurality of blocks if it exceeds a predetermined size. Block identification numbers are assigned to the divided blocks, respectively. Then, a size of a desired one of the divided blocks is set. In a reception mode, a counterpart station identification number and a desired one of the block identification numbers are set. Also, a common reception region is set. Then, an individual reception region is set as needed. After the transmission and reception parameters are set, they are read whenever a user's program is completed. Data transmission and reception operations are performed according to the read transmission and reception parameters.