1. An apparatus for reducing image noise with filter matrix, comprising: a first input unit for receiving input of an object image data for conversion; a second input unit for receiving input of a size data of a conversion area of the image data; a first output unit for setting conversion unit matrixes that are movable in the conversion area in a predetermined direction relative to a standard matrix, namely, a reference matrix for conversion; a second output unit for outputting average values of image information of pixels corresponding to the conversion unit matrixes set by first output unit and outputting an average value of image information of pixels corresponding to the standard matrix; an arrangement unit for calculating difference values between the average value of the standard matrix and the average values of the conversion unit matrixes and arranging the calculated difference values according to size; and a conversion unit for low-pass filtering the conversion unit matrixes having difference values smaller than a predetermined ordinal number among the arranged difference values.