An apparatus for forming a film by the CVD method allows reaction products to be easily removed from a gas discharge surface without decreasing the uptime/downtime ratio, and includes a gas distributor having a gas discharge surface for discharge of a reaction gas for forming a film on a substrate. A wafer holder has a wafer mounting surface facing the gas discharge surface. A cleaner has a suction head and a brush formed at the entrance of the suction head. A rotary shaft supports the cleaner for movement between the gas discharge surface and a stand-by position and brings the brush of the cleaner onto the gas discharge surface. A vertical positioner moves the wafer holder or gas distributor upward or downward, whereby the wafer holder approaches the gas discharge surface for forming a film and is spaced from the gas discharge surface when cleaning the gas discharge surface by movement of the cleaner on the gas discharge surface.