Organic-inorganic hybrid coating films were prepared using vinyltriethoxysilane and tetraethoxysilane by the sol-gel method on polyimide substrates. Tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) or polyvinyltriethoxysilane (PVTES), which was obtained by the radical polymerization of VTES, were used as starting materials. In the TEOS-PVTES system, the organic-inorganic hybrid films with both carbon-carbon and siloxane bonds were obtained, and PVTES gave crack-free and flexible films over a wide composition range. It was found that the Si-O-Si bonds in the organic-inorganic hybrid films contributed to the increase in the dynamic hardness, while the smoothness of the coating films prepared using PVTES contributed to the increase in the pencil hardness.