The effects of the binaural auditory filter in the human auditory cortex were examined by auditory-evoked magnetic fields. Two tones with different frequency separations, which were presented dichotically to the left and right ears, were used as the sound stimuli, with all signals presented at sound pressure level of 60 dB. The results indicated that the N1m amplitudes were approximately constant when the frequency separation was less than 100 Hz; however, the N1m amplitudes increased with increasing frequency separation when the frequency separation was greater than 200 Hz. These findings indicate that binaural auditory filter-like behavior might be reflected in N1m amplitudes.