When plasma processing is finished, a gate valve 13a is closed and cleaning gas is ejected from holes 121a of a shower plate 121, and at the same time, a microwave is generated from a microwave generator 101. Further, at this time, the inside of a process chamber 110 is exhausted through a second exhaust port 106. Since the exhaust is conducted through a second exhaust port 106 positioned lower than a wafer stage 104 in a lowered state when the inside of the process chamber 110 is cleaned, it is possible to more effectively remove gas and reaction products deposited especially in a lower portion of the process chamber 110.