A noise reduction circuit and method effectively reduce noise with a simple structure regardless of the partial content of an image while suppressing an increase in the capacity of the image memory used and process delays. The present invention forms noise-reduced data by utilizing a correlation between from the difference between a pixel subjected to noise reduction and data of a pixel that is shifted by a predetermined amount in a time direction and/or spatial direction, and forms a difference cause discriminating signal indicating whether the difference is due to a valid change of the image. The noise-reduced data and the difference cause discriminating signal are formed for a plurality of different correlations. Final noise-reduced video data are obtained by selecting a method for determining the final noise-reduced video data based on the difference cause discriminating signals, and accordingly selecting/combining the plurality of noise-reduced data.