An object is to provide a turbine housing assembly in which reduction of weight, facilitation of manufacture, cost-cutting, and reduction of heat capacity are further promoted compared to a conventional turbine housing made of sheet metal. A turbine housing assembly includes a plurality of constituent members connected to one another to constitute a turbine housing into which a turbine wheel is inserted. The turbine housing assembly at least includes a scroll part 2 and an exhaust part 8 of a tubular shape having a separate body separate from the scroll part 2. The scroll part 2 is formed by processing a single piece of sheet metal so that, on a back face side of a bottom face part 22 of the scroll part 2, a recess portion 22b on which a through-hole of an exhaust gas outlet 2B is formed and a projecting portion 22a formed by a bottom surface of an exhaust gas flow path 2A projecting toward the back face side are formed, the projecting portion 22a surrounding the recess portion 22b. The recess portion 22b of the scroll part 2 is connected to an end portion 8a of the exhaust part 8 in a turbine axial direction so that the exhaust part 8 is in communication with the exhaust gas outlet 2B of the scroll part 2 in a state where a gap “a” is formed between an outer circumferential face of the exhaust part 8 and the projecting portion 22a of the scroll part 2.