1. An image processing method for reducing noise of an image to be filtered by determining a noise reduction filter coefficient and calculating weighted sum, with the coefficient, of the pixel values of a focus pixel and its surrounding reference pixels of the image, comprising: a step of determining a first coefficient of the noise reduction filter by using the difference in pixel values and relative position between a focus pixel and each of its surrounding reference pixels in the source image where the source image is the target image to be filtered; a step of creating a smoothed image by smoothing pixel values within a surrounding area for each pixel in the source image; a step of determining a second coefficient of the noise reduction filter by using the difference in pixel values and relative position between a focus pixel of the source image and a pixel extracted, by every predetermined number of pixels, from the smoothed image; and a step of computing the compensated pixel value of the focus pixel in the source image with weighted sum of each pixel value applying the first coefficient to the reference pixels and the second coefficient to the pixels detected from the smoothed image.