An apparatus for reducing image noise with filter matrix comprises 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 convention area; a first output unit for setting conversion unit matrixes movable in the conversion area in a predetermined direction relative to a standard matrix; 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 calculation (difference) values according to size; and a conversion unit for low-pass filtering the conversion unit matrixes having calculation values smaller than a predetermined ordinal number among the arranged calculation values.