To provide an air supply/exhaust top having small exhaust resistance and capable of properly preventing inflow of much air of low oxygen concentration including much exhaust gas to an air supply opening in receiving the wind in a specific direction.

This air supply/exhaust top T1 includes a communication pathway 52 for guiding a part of the exhaust gas flowing out from a distal end opening section 20 of an exhaust stack 2 to a region at a distal end side with respect to a cover section 4 in a spatial section 50 in a cylindrical wall section 5, and a top plate section 6 provided with a second exhaust opening 62 for discharging the exhaust gas passing through the communication pathway 52 to the external. The top plate section 6 has a first region A1 corresponding to a region on a straight line L connecting a center O of the exhaust stack 2 and the first exhaust opening 51 and its peripheral region, and a second region A2 excluding the above in a shaft length direction view of the exhaust stack 2, and in the second exhaust opening 62, an aperture ratio in the second region is smaller than that of the first region A1.