A noise reduction apparatus in accordance with the present invention is configured to reduce mosquito noise while retaining edges by calculating the maximum value Y of the difference values of adjacent pixels in an area of MN around a notice pixel by using a difference value calculator and a maximum value calculator, by controlling a pixel replacement device depending on Y and the difference value X from the notice pixel in the area of JK narrower than the area of MN, and by carrying out more intense smoothing depending on the magnitude of X with respect to Y, that is, when X is smaller than Y.