This paper proposes a method for robustly and accurately estimating fundamental frequency (F0) of the steady complex tone on the basis of an amplitude modulation/demodulation technique. It is based on the well-known mechanism of pitch perception for AM tone. The comparative results revealed that the percentage correct rates of the estimated F0s using a few recent methods (TEMPO, PHIA, and CmpCep) were drastically reduced as the SNR decreased and as the reverberation time increased. The results also demonstrated that the proposed method robustly and accurately estimated F0 in both noisy and reverberant environments.