To provide a noise reducing method and device that detect a noise component included in a digital video signal and perform proper noise reduction.

Disclosed are the method and device which, when comparing a digital input image signal with an output image signal one frame precedent to detect a noise, decide that there is a noise when |a-b|≤x and a-b≠1, where (a) is an input image signal, (b) is an output image signal one frame precedent, and (x) is a predetermined reference value, and average both the image signals when there is the noise and output the input image signal as it is when not.