Photon-echo quantum beats arising from magnetic splitting of the cesium $7{P}_{\frac{3}{2}}\ensuremath{-}6{S}_{\frac{1}{2}}$ transition were observed in a dilute atomic vapor by means of a novel polarization-rotation technique. The quantum-beat spectrum contains frequencies generated by the hyperfine structure of the
7P23 level as well as those due to the Zeeman splitting of both ground and excited levels. Experimental data for both
F=3 and
F=4 hyperfine components of the
6S21 ground state and for several echo delay times were fitted to calculated spectra, including corrections arising from Faraday rotation of the echo pulses.