A plasma processing apparatus is provided that is configured to supply a gas into a chamber, generate a plasma from the gas using a power of an electromagnetic wave, and perform a predetermined plasma process on a substrate that is held by a mounting table. The plasma processing apparatus includes a dielectric window through which the electromagnetic wave that is output from an electromagnetic wave generator is propagated and transmitted into the chamber, a support member that supports the dielectric window, a partition member that separates a space where the support member is arranged from a plasma generation space and includes a protrusion abutting against the dielectric window, and a conductive member that is arranged between the partition member and the dielectric window and is protected from being exposed to the plasma generation space by the protrusion.