A channel map generation method includes: performing a power spectrum density detection on a plurality of channels in a frequency band, to generate a first channel map; and performing a first smoothing operation on the first channel map by a first window size to generate a second channel map. The first smoothing operation includes: grouping channels of the first channel map into a plurality of channel groups according to the first window size; and according to the number of good channels or bad channels in each of the channel group, deciding to retain channel determinations in the first channel map of the channel group, or re-designating all the channels of the channel group, so as to generate the second channel map.