PROBLEM TO BE SOLVED: To provide a butterfly valve which has a long service life and generates less dust. SOLUTION: A closed body 32 comprises a main shaft 40, which is mounted inside of a valve housing 12 and rotatably around a longitudinal shaft 42 between an open position and an intermediate position, a crankshaft 110 which is rotatable around the longitudinal shaft 42 between the open position and a closed position, a hub 60 which is mounted on the main shaft 40 and allows transitional movement of a sealing plate body with respect to the hub 60 by being connected to the sealing plate body, so as to be movable, a ball bearing 122 which is engaged with the sealing plate body and mounted on the crankshaft 110 to be eccentrically rotatable around the longitudinal shaft 42, and one or more springs which connect the sealed plate body to the hub 60 to energize a sealed plate 70 towards the intermediate position. A butterfly valve may be provided with a valve actuator 34 adapted to rotate the crankshaft 110 around the longitudinal shaft 42 between the open position and the closed position.