PURPOSE: To prevent the occurrence of condensation to the external part of a valve shaft cylinder and the outer surface of an actuator through disconnection of transmission of a low temperature from fluid to be controlled by providing a transfer heat disconnecting part formed of only a heat insulation resin material between the external part of a valve shaft cylinder exposed to the atmosphere without being covered with a heat insulation cover and the internal part covered with the heat insulation cover.

CONSTITUTION: A butterfly valve 10 comprises a valve body 11 made of a metal wherein a cylindrical fluid passage is partitioned; a disc-form valve body 13 rotatably disposed in the valve body; a seat ring 14 formed of a seal material with and from which the outer peripheral surface of the valve body makes contact and parts; a pair of valve rods 15 on the drive side and the floating side extending from the radial opposite position of the valve body to the outside; and a pair of valve shaft cylinders 16. Thus, the valve shaft cylinder on the drive side ends in the middle to form an internal part, the external part of the valve shaft cylinder on the drive side is formed of a heat insulation resin material and formed integrally with the internal part, and a transfer heat disconnecting part is arranged in such a state to make contact with the final end of the valve shaft cylinder on the drive side.