To provide a rotary valve in a simple structure, capable of preventing the occurrence of any deviation between a casing body and an end cover, and preventing any inclination or eccentricity of a rotary shaft member even when the casing body is exposed to a high-temperature state.

Both joining surfaces 36 and 38 are joined with each other so that an annular groove 39 of an end cover 19 for closing the open end of a casing body 15 is fitted to an annular projecting part 37 of the casing body 15, and in this state, the end cover 19 is fitted to the end of the casing body 15 by a fastening bolt 18. When the casing body 15 is exposed to a high-temperature state and thermally inflated, the outer circumferential surface of the annular projecting part 37 and the outer circumferential surface of the annular groove 39 are firmly and tightly attached to each other. On the other hand, when the casing body 15 is thermally shrunk in a low-temperature state, the inner circumferential surface of the annular projecting part 37 and the inner circumferential surface of the annular groove 39 are firmly and tightly attached to each other.