PURPOSE: To provide a fault-state specifying apparatus, which can spot the fault of a transmission line highly accurately pegardless of the number of terminals, the number of circuits and measuring points.

CONSTITUTION: A current transformer CT detects the current of each sending terminal, which is attached to a transmission line. A transformer PT detects a voltage. A terminal device 100 has an operating and processing device 220, which has the program for analyzing a circuit equation at the time of the fault of a transmission section based on the measured data of both detecting means CT and PT and the circuit equation for a generator G of the electric power system and the load L of the generator at the time of the fault. The operating and processing device 220 analyzes both equations with the analyzing program. Thus, the spotting accuracy is improved.