To provide a noise monitoring/eliminating circuit capable of selecting the optimum filter in accordance with the noise change of an installation environment or the like.

Power input from a power input terminal 11 to a filter part 12 is branched to a plurality of filters and then is output from each filter to a switch part 13 and a detection part 14. The power input from the power input terminal 11 to the detection part 14 is smoothed by a plurality of detectors and then is output to an analog/digital conversion part 15 as analog signals. The analog signals input to the analog/digital conversion part 15 are converted to digital signals by a plurality of A/D converters, and the digital signals are output to a control part 16. The digital signals input to the control part 16 are compared with a preliminarily set signal, and a switch control signal corresponding to comparison results is output to the switch part 13.