In-situ monitoring of film quality of the diamond film during growth by hot filament-assisted CVD method is made. The CVD diamond film including non-diamond carbon was grown under the condition where the current flows between a filament and a substrate. On the other hand, the almost pure CVD diamond film was grown under the condition where no current flows between a filament and a substrate. The intensities of thermoelectron emission and secondary electron emission from CVD diamond including non-diamond carbon are higher than those from CVD diamond films including nondiamond carbon. Defect density with lone-pair electron in CVD diamond films including nondiamond carbon was about five times higher than that of the pure CVD diamond films. It was suggested that electrons mainly emit from lone-pair electron defects on the surface of CVD diamond films including nondiamond carbon.