The contactless electroreflectance¡]CER¡^ spectra of ZnO bulk has been measured at 300K. It was observed the difference between the CER spectra by using the polarization E of probe light perpendicular ( E¡æc) and parallel ( E¡üc) to the c-axis of the m-plane ZnO. In addition, a mercury lamp was focused on the sample to reduce its strength of electric field. It was observed that the CER spectrum was blue-shifted with Hg lamp being on. Hence, the observed features were attributed to excitonic transitions. The experimental spectra were fitted by Lorentzian lineshapes. The energies of the A ( B¡^, B¡]A¡^, and C excitonic transitions were determined as 3.329eV, 3.343eV and 3.387eV, respectively.