A noise reduction apparatus includes a noise reduction amount calculator. The noise reduction amount calculator includes a difference calculator that obtains a difference between a level of the noise detected by a first noise detecting microphone and a level of the noise detected by a second noise detecting microphone when control sound is not output, a storage unit that stores the difference, an estimated noise value calculator that estimates a noise level that is to be detected by the second noise detecting microphone when the control sound is output, based on the level of the noise detected by the first noise detecting microphone when the control sound is output and the difference, and a reduction amount calculator that calculates a noise reduction amount on the noise reduction target position, based on the estimated noise value and the level of the noise detected by the second noise detecting microphone when the control sound is output.