Plasma processing apparatus

A plasma processing apparatus is provided with: a processing chamber (2); and a gas supply device (30) for supplying a processing gas to the inside of the processing chamber (2). A gas supply device (30) is provided with: a mass flow controller case (40) having an intake port (41) and an exhaust port (42); a plurality of pipes (43) to which the mass flow controllers (43a) are mounted; and a plurality of pipes (52) that are connected to the plurality of pipes (43) inside the mass flow controller case (40) and that are connected to the plurality of pipes (54), which are the supply sources of the processing gas, outside the mass flow controller case (40) by means of a plurality of couplers (53). At least one of the plurality of couplers (53) is covered by a piping cover (60) so as to seal the couplers (53). The inside of the pipe housing (60) and the inside of the mass flow controller case (40) are communicated with each other by a communication member (outer peripheral pipe (61), pipe (62)). 等离子处理装置具备：处理室(2)；和用