1. An image processing method of reducing noise from moving images which are input at intervals of a predetermined time unit, comprising the steps of: compensating a motion of an image that has been processed one predetermined time unit before block by block; determining reliability of addition of a current moving image and the motion-compensated image processed the one predetermined time unit before pixel by pixel and setting a weighting factor corresponding thereto; adding or averaging the current moving image and the motion-compensated image processed the one predetermined time unit before with the weighting factor and obtaining a processed image corresponding to the current moving image; and first correcting the weighting factor that is output from determining reliability step, wherein the correcting step is performed by detecting a case of which block distortion occurs in the processed image; and second correcting the weighting factor such that the detected block distortion is reduced.