There is disclosed a method for cleaning a component of a plasma processing apparatus which is disposed in an inner space defined by a processing chamber of the plasma processing apparatus. The cleaning method comprises: forming a film on the surface of the component, wherein a compound forming the film is generated by polymerization of a first compound contained in a first gas and a second compound contained in a second gas, the first compound being isocyanate and the second compound being amine or a compound having a hydroxyl group; transferring the component from the processing chamber to a heating chamber after substrate treatment is performed in the inner space; and heating the component so that depolymerization of the compound forming the film occurs.