The kinetics of cristobalite growth on polycrystalline beta-SiC films at 1803 and 1873 K were investigated. Sample films were synthesized on graphite strips via chemical vapor deposition and heated in air by their electric resistance. It was demonstrated that in situ X-ray diffractometry using imaging plate was useful for analyzing the growth of the oxide crystals with the coexistence of amorphous silica. The kinetics were found to obey parabolic laws. This is consistent with oxidation kinetics of SiC reported earlier.