There is provision of a method of cleaning an exhaust pipe of a film forming apparatus for removing a component adhering to the exhaust pipe which is generated from a source gas for forming film supplied from a gas supply part to a processing chamber of the film forming apparatus. The method includes a step of supplying a cleaning gas directly, from a cleaning gas supply part disposed near a joint between the processing chamber and the exhaust pipe, to the exhaust pipe without passing through the processing chamber, in order to remove the component by causing the component to vaporize upon reacting with the cleaning gas. The cleaning gas to be supplied is capable of causing the component adhering to the exhaust pipe to change into an evaporable substance by chemical reaction in an atmosphere inside the exhaust pipe.