A plasma stream-derived deposited matter formed on an annular rib for droplet capture in a plasma processing apparatus is prevented from falling into a plasma generation portion and causing a short circuit. The annular rib for the droplet capture is divided into multiple rib segments. Thus, from the beginning of the formation of the deposited matter on the annular rib due to the aggregation of the material in the plasma stream, it is possible to reduce the size of the deposited matter. By reducing the size of this deposited matter, when a piece of the deposited matter falls into the plasma generation portion, the piece of the deposited matter gets into a groove portion provided between a cathode and a wall surface of the plasma generation portion, thereby preventing the electrical short circuit between the cathode and the wall surface.