A fault current detecting circuit, comprising: a current detection unit configured to detect a current flowing in an electric power circuit in an electric power system and output a current detection signal; a first comparing circuit unit configured to compare the current detection signal with a predetermined reference current value and output a first output signal when the current detection signal is greater than or equal to the reference current value; a differentiator configured to differentiate the current detection signal output from the current detection unit to output a change slope of the current detection signal; a second comparing circuit unit configured to compare the change slope with a predetermined reference change slope value and output a second output signal when the change slope of the current detection signal is greater than or equal to the reference change slope value; and a trip determining unit connected to the first comparing circuit unit, and the second comparing circuit unit to receive the first output signal and the second output signal, characterized in that the fault current detecting circuit further comprises a thir d comparing circuit unit configured to compare the current detection signal with a predetermined current detection limit reference value and output a third output signal when the current detection signal is greater than or equal to the current detection limit reference value and the trip determining unit is connected to the third comparing circuit unit to receive the third output signal, and output a trip control signal only when the first output signal and the second output signal are maintained to be received and the third output signal is not received during a predetermined short period of time starting from a time point in time at which the first output signal and the second output signal are simultaneously received, wherein the predetermined short period of time is determined as a value ranging from 50 microseconds, us, to 100 us. a current detection unit configured to detect a current flowing in an electric power circuit in an electric power system and output a current detection signal; a first comparing circuit unit configured to compare the current detection signal with a predetermined reference current value and output a first output signal when the current detection signal is greater than or equal to the reference current value; a differentiator configured to differentiate the current detection signal output from the current detection unit to output a change slope of the current detection signal; a second comparing circuit unit configured to compare the change slope with a predetermined reference change slope value and output a second output signal when the change slope of the current detection signal is greater than or equal to the reference change slope value; and a trip determining unit connected to the first comparing circuit unit, and the second comparing circuit unit to receive the first output signal and the second output signal, characterized in that the fault current detecting circuit further comprises a thir d comparing circuit unit configured to compare the current detection signal with a predetermined current detection limit reference value and output a third output signal when the current detection signal is greater than or equal to the current detection limit reference value and the trip determining unit is connected to the third comparing circuit unit to receive the third output signal, and output a trip control signal only when the first output signal and the second output signal are maintained to be received and the third output signal is not received during a predetermined short period of time starting from a time point in time at which the first output signal and the second output signal are simultaneously received, wherein the predetermined short period of time is determined as a value ranging from 50 microseconds, us, to 100 us.