To simplify the assembling work of valve shaft and drive shaft by supporting a cylindrical body made of wear resistant resin to an end of a valve case or actuator so as to be rotatable, fitting the end of the valve shaft and actuator drive shaft in from the direction opposite to the cylindrical body, and making an engaging part engage.

In a mounting hole 6 formed at an end of a valve casing 1 a cylindrical body 7 made of florine resin is fitted loosely so as to be rotatable. Engaging parts 8, 9 engaging with each other are formed at end of valve shaft 3 and actoator drive shaft 5 are formed, and the ends of the shafts 3, 5 are inserted from the mutually opposite directions of the cylindrical body 7 for allowing the engagement parts to engage with each other, thereby carrying out centering. The cylindrical body 7 is supported into the hole 6 so that the axis thereof corresponds to the axis of the valve shaft 3 and actuator drive shaft 5, thereby enabling an easy centering. Accordingly the assembling work for connecting the shafts 4, 5 is made easy in a short time, assuring a simple disassembling wok for maintenance.