In the cathodoluminescence (CL) spectra of natural II diamond and high-quality chemical vapor-deposited diamond, both a free-exciton recombination radiation peak originating from high crystallinity (perfection of the crystal structure) and a band A peak originating from low crystallinity (imperfection of the crystal structure) are observed. In this study, a homoepitaxial diamond film is synthesized on a single-crystal diamond (100) substrate by the combustion flame method, and the film quality is evaluated by CL analysis. Crystal defects are mechanically introduced into the diamond film to study changes in the CL spectrum and the following results were obtained. (1) High-quality diamond with negligible amounts of nitrogen impurities and crystal defects can be synthesized at a high rate (100 m/h) using the combustion flame method. (2) The band A peak corresponding to a crystal defect is broad, with a wavelength of 430 nm. (3) Mechanically introduced cracks (crystal defects) decrease the intensity of the FETO peak, while the intensity of the band A peak increases.