A plasma processing apparatus includes a mounting stage including a mounting surface, on which an object to be processed is mounted, a back surface provided on a side opposite to the mounting surface, a plate-like member, in which a first hole penetrating through the mounting surface and the back surface is formed, and a base having a supporting surface for supporting the plate-like member and having a second hole communicating with the first hole; and an embedment member disposed inside the first and second holes, the first embedment member being disposed inside the first hole, the second embedment member being disposed inside the second hole, wherein the first embedment member and the second embedment member are not mutually fixed, and the first embedment member has a portion having a wider width than a width of an upper end portion on a lower side than the upper end portion.