The present disclosure relates to a noise reduction device and a noise reduction method capable of reducing noise in a more stable and effective manner. Signal processing is performed to generate a reference signal representing a waveform of noise. Moreover, signal processing is performed for an error signal representing a waveform of an error measured by a microphone in accordance with an amplitude-frequency characteristic. Then, a filter coefficient with which the error signal becomes zero is calculated under adaptive algorithm with reference to the reference signal. The reference signal is filtered by using the filter coefficient to obtain a control signal. The control signal is supplied to the corresponding one of the predetermined number of output units. The present technology is applicable to a noise cancelling system equipped in a closed space such as an interior of a vehicle, for example.