A device for outputting a luminance signal and a method thereof are disclosed. The device includes an image smoothing unit, a band pass filter unit, and a summing unit. The image smoothing unit receives a 2D luminance signal and decreases a signal intensity of a component of the 2D luminance signal within a frequency range with respect to a carrier frequency of a chrominance component. The band pass filter unit passes the component of the 2D luminance signal within the frequency range with respect to the carrier frequency. The summing unit sums the output of the image smoothing unit and the output of the band pass filter unit to generate a resultant luminance signal. The present invention is capable of avoiding the occurrence of saw-tooth or sparkling situation caused by inharmonious switching between a 1D comb filter and a 2D comb filter.