A protection relay device for judging whether an accident point of a power system exists within a specified range, comprising: filter components 1 and 2, for inputting sampling data of voltage and current of the power system into a digital filter having a specified transfer function, Output the first voltage data and the first current data and the second voltage data and the second current data which are orthogonal to the first voltage data and the first current data respectively; the calculation parts 3, 5, 7 and 9, according to the first time the first voltage data, the first current data, the second voltage data, the second current data, and the first voltage data, the first current data, the second voltage data, the first voltage data, the first current data, the second voltage data, the first time two current data to calculate a prescribed measurement value; and an operation judging part, which performs an operation judgment according to the prescribed measurement value obtained by the calculation part. Even if the high-frequency components are generated in the accident voltage and current of the power system, the present invention is not affected, and the reliability can be improved.