To arbitrarily adjust the movement amount of an opening indication portion changing according to the rotation amount of a handle.

A first gear 73 and a third gear 74 are supported on a support member 42 rotated when the operation handle 5 is operated. The first gear 73 is meshed with a second gear 63 secured to the body side of the open/close valve 2. The third gear 74 is meshed with the fourth gear 64 of an indication member 61 rotatably supported on the operation handle 5. A cover 62 for indicating the opening by the change of the relative position thereof to the indication member 61 is installed over the operation handle 5. When the operation handle 5 is rotated, the first gear 73 is rotated by the second gear 63, and the third gear 74 rotates the indication member 61 through the fourth gear 64. The opening of the open/close valve according to the rotation amount is indicated by the positional relation of the indication member 61 relative to the cover 62.