A plasma processing apparatus capable of reducing the use amount of a dielectric member is provided. The plasma processing apparatus 1 includes a metal processing chamber 4 configured to accommodate therein a substrate G to be plasma-processed; an electromagnetic wave source 34 that supplies an electromagnetic wave necessary to excite plasma in the processing chamber 4; one or more dielectric members 25 provided on a bottom surface of a cover 3 of the processing chamber 4 and configured to transmit the electromagnetic wave supplied from the electromagnetic wave source 34 into the inside of the processing chamber 4, a portion of each dielectric member 25 being exposed to the inside of the processing chamber 4; and a surface wave propagating section 51 installed adjacent to the dielectric member 25 and configured to propagate the electromagnetic wave along a metal surface exposed to the inside of the processing chamber 4.