PURPOSE: To provide a noise reducing device capable of widening the dynamic range of a noise control by enabling reducing a noise regardless the magnitude of the noise level.

CONSTITUTION: A noise 4a generated by a noise source 1 is detected by a pickup microphone 2 and the level of the noise is corrected by a variable gain amplifier 11a, a scale factor adjusting part 12a, a gain control part 13a to be inputted to an ANC arithmetic part 14. Similarly, the level of a sound in a muffling area detected by an error detecting microphone 5 is corrected by a variable gain amplifier 11b, a scale factor adjusting part 12b, a gain control part 13b to be inputted to the ANC arithetic part 14. A sound erasing signal induced out by an ANC operation in the ANC arithmetic part 14 is corrected by a scale factor adjusting part 16 and a variable gain amplifier 17 to drive a speaker 3, which generates an erasing sound 4b having the same amplitude as that of the noise 4a and having a phase opposite to that of the noise 4a and then the erasing sound 4b reduces the noise in the muffling area.