1. An image processing method of using a first still image and a second still image which are chronologically successive and outputting an image from which noise has been reduced, comprising the steps of: compensating a motion of the second still image block by block; determining reliability of addition of the first still image and the motion-compensated second still image pixel by pixel and setting a weighting factor corresponding thereto; and adding or averaging the first still image and the motion-compensated second still image with the weighting factor and obtaining a processed image.