In a protective relay device for a three-terminal transmission line comprising terminal A, terminal B and terminal C, when for example terminal information is transmitted to a protective relay Ry-A of one remote terminal (terminal A) from the protective relay Ry-C of the terminal C, terminal information Db that was sent from the protective relay Ry-B of another remote terminal (terminal B) is transmitted, in addition to the information Dc of the terminal in question. In the same way, when terminal information is transmitted to a protective relay Ry-B of the terminal B from the protective relay Ry-C of the terminal C, terminal information Da that was sent from the protective relay Ry-A of the terminal A is transmitted, in addition to the information Dc of the terminal in question.