A plasma processing system includes a chamber, a gas supply unit, a gas exhaust unit, a separating unit, a boost unit and an accumulation unit. The chamber is configured to process a target substrate by plasma of a gaseous mixture of a rare gas and a processing gas. The gas supply unit is configured to supply the rare gas and the processing gas into the chamber. The gas exhaust unit is configured to exhaust a gas containing the rare gas from the chamber. The separating unit is configured to separate the rare gas from the gas exhausted by the gas exhaust unit. The boost unit is configured to boost the rare gas separated by the separating unit. The accumulation unit is configured to accumulate the rare gas boosted by the boost unit and supply the accumulated first rare gas to the gas supply unit.