When two electromagnetic plane waves of different frequencies, f_1 and f_2,are incident upon a semi-infinite, anisotropic plasma, mixing phenomena of the electromagnetic waves are theoretically considered. For the simplicity, the waves are assumed to be vertically incident upon the plasma, and the static magnetic field is also assumed to be parallel to the direction of the wave propagation. In the plasma, the second order fluctuations of electron density of frequencies 2f_1,2f_2,|f_1±f_2| are excited as well in the anisotropic plasma as in an isotropic case. The plasma resonance of the difference frequency wave takes place, when |f_1-f_2|=f_p, where f_p is the plasma frequency. In this case, the amplitude of the difference frequency wave is affected by the cyclotron frequency of the plasma. And the amplitude becomes larger as the cyclotron frequency becomes higher. The effect of the collision frequency on the resonance phenomenon is also reported in this paper.