The present disclosure relates a method of detecting an electrical disturbance by a DC component in a digital protective relay, which includes acquiring a sample value by sampling an input signal at a regular cycle, detecting the electrical disturbance based on a difference between a sampled first sample value and a second sample value after the first sample value, and when the electrical disturbance is detected, detecting the DC component based on a difference between the second sample value and a third sample value after the second sample value and a difference between the third sample value and a fourth sample value after the third sample value.