A processing system 1 comprises: a processing vessel 30 configured to accommodate an object to be processed W in a processing space 83; a process-fluid generating part 41 configured to generate a process fluid of a predetermined temperature; and a main duct 56 arranged between the process-fluid generating part 41 and the processing vessel 30, the main duct 56 being configured to guide the process fluid supplied from the process-fluid generating part 41. A process-fluid supply duct 171 is arranged on a downstream side of the main duct 56 via a switching valve 70, the process-fluid supply duct 171 being configured to introduce the process fluid into the processing space 83 of the processing vessel 30. A process-fluid bypass duct 172 is arranged on the downstream side of the main duct 56 via the switching valve 70, the process-fluid bypass duct 172 being configured to guide a process fluid, which is not introduced to the process-fluid supply duct 171, so as to bypass the processing space 83. The main duct 56 is provided with a flow-rate adjusting mechanism 65 for adjusting a flow rate of the process fluid flowing through the main duct 56.