PURPOSE: To improve a sealing property of a revolving valve of a ball valve, etc., by using a bellows.

CONSTITUTION: A valve stem 9 to revolve a valve body 6 is inserted into a valve cylinder communicated to a valve chest 2, an outward collar 12 is provided on the valve stem 9, a bellows 16 is engaged with the valve stem 9, one end of the bellows 16 is connected to a holding ring 15 installed on a valve cylinder in the sealed state, and the other end of the bellows 16 is connected to a pressing ring 17 made in contact with the outward collar 12 through a seal ring 19 in the same way. The seal ring 19 tightly presses the outward collar 12 through the pressing ring 17 by elasticity of the bellows 16.