A method of maintaining a processing device having an upper electrode unit structuring a ceiling portion of a processing chamber, and a lift mechanism which can raise and lower the upper electrode unit, and the upper electrode unit is structured from a lower assembly at a processing chamber side and an upper assembly at a power supply side, and the lower assembly and the upper assembly can be separated and united by only a lock mechanism provided at an outer peripheral surface of the upper electrode unit, and the lower assembly can be airtightly fixed to the ceiling portion of the processing chamber by differential pressure between an interior and an exterior of the processing chamber and weight of the upper electrode unit without a mechanical mechanism, said method comprising the step of:
- maintaining the interior of the processing chamber after the upper assembly and the lower assembly are integrally raised by the lift mechanism in a state in which the lock mechanism is locked.