To provide a noise distortion correction filter for a communication line for effectively correcting time waveform distortion occurring in a communication signal flowing in the communication line by electromagnetic noise from the outside, and to provide a method of correcting noise distortion for the communication line.

A signal separation section 12 detects the communication signal flowing in the communication line 200 and a detection signal detected by a sensor section 17 as a plurality of detection signals, uses an independent component analysis method to calculate a plurality of estimation signals estimated as an original signal and an electromagnetic noise signal from the plurality of detection signals, and separates the plurality of estimation signals from the plurality of detection signals as the plurality of separation signals. A similarity calculation section 14 calculates similarity between respective detection and separation signals. A signal application section 15 decides separation signals corresponding to the respective detection each based on the similarity.