It is intended to provide a composite structure excellent in resistance characteristics such as plasma resistance. The composite structure includes a base material having a surface containing a ceramic polycrystal and a structure formed on the surface of the base material containing the ceramic polycrystal, wherein the structure contains a polycrystal containing a brittle material; a grain boundary layer having a glass layer does not substantially exist on a boundary face between crystals forming the polycrystal; a part of the polycrystal forms an anchor part embedded into the base material surface; and an average roughness (Ra) of an interface between the anchor part and the base material surface is 100 nm or less.