To reduce the sound of airflow generated by a gas that passes at high speed through a gap between a valve disc and a valve body when a butterfly valve is closed.

In this butterfly valve 11 having a valve body 13 forming a part of a gas passage 2, a valve element 4 placed within the valve body 13, a rotating shaft 5 having the valve element 4 secured thereto, and cylindrical bearing members freely rotationally supporting the rotating shaft 5 when fitted into two rotating shaft supporting holes formed in the valve body 13, spherical portions 14 are formed on the upstream and downstream sides of the inner peripheral surface of the valve body 13 including an area opposite to the valve element 4 rotated by the rotating shaft 5, and a single or plural pressure variation regulating grooves 15 are formed from the center to the upstream side of each spherical portion 14. The pressure variation of gas that passes is regulated by the rotation of the valve element 4 and the airflow sound of the passing gas is reduced when the butterfly valve 11 is fully closed.