1. An image processing system which performs noise reducing process with respect to an image signal formed of a plurality of color signals from an image pickup device, comprising: extraction means for extracting a local region which contains a target region to be subjected to the noise reducing process, and at least one or more neighborhood regions which exist neighborhood of the target region from the image signal; vectorizing means for obtaining vector signals which contain the plurality of color signals as components for each of the target and the neighborhood regions; set means for setting weighting factors with respect to each of the vector signals in the local region based on the vector signal in the target region; filtering means for performing a filtering process using the weighting factors with respect to the vector signals in the local region; and noise reducing means for reducing a noise of the vector signal in the target region based on the vector signal through the filtering process.