PURPOSE: To remove a mosquito noise, which is generated at the time of high compression in the case of image compression-encoding due to orthogonal transformation, in a small circuit scale while reducing the degradation of resolution.

CONSTITUTION: This device is provided with a means 12 for deciding the size of vertical unevenness near the picture element of an input image signal for each picture element and a vertical adaptive filter processing means 1 for selectively outputting the output of a vertical logical filter 11 corresponding to the picture element of the pixel signal while using a selector 13 when it is decided that the unevenness is small. Further, this device is provided with a means 22 for deciding the size of horizontal unevenness near the picture element for each picture element and a horizontal adaptive filter processing means 2 for selectively outputting the output signal of a horizontal logical filter 21 corresponding to the picture element of the pixel signal while using a selector 23 when it is decided that the unevenness is small. Thus, the mosquito noise can be removed in the small circuit scale while reducing the degradation of resolution. Further, not only the noise at the flat part of an image but also the noise on any line segment or edge can be removed without blurring the line segment or edge.