The reflection spectra from the side face of a PbSb2Te4 crystal were measured by room temperature in polarized light in the range 50-4000 cm-1. Significant anisotropy of the crystal is shown in the directions along and across the crystal layers. The revealed spectral features are interpreted by the contribution of plasma oscillations and crystal lattice vibrations. The calculated dielectric function parameters in the framework of the Drude-Lorentz model are consistent with experimental data.