This paper describes the muon identification method and its performance in the Belle experiment at KEKB. Muon and hadron likelihood are calculated for each track using its range and transverse scattering in the KL-and-muon detector (KLM). We apply a cut on the normalized muon likelihood Lμ to identify the track as a muon. Above the detection threshold of 0.6GeV/c, the measured muon detection efficiency and pion fake rate are approximately constant for momenta greater than 1.0 and 1.5GeV/c, respectively. Between 1.0 and 3.0GeV/c, the averaged muon detection efficiency is 89% and the pion fake rate per track is 1.4% over the KLM acceptance, using the standard selection criterion Lμ>0.9.