To provide an operation valve having higher durability in the operation valve arranged in a flowing passage of corrosive gas.

In this operation valve for housing this diaphragm 4 for opening and closing this opening by abutting to the opening 252 formed in the center of a valve seat 231 in a valve chest 23 in a valve body 2 having the valve chest 23 arranged between a gas inflow passage 25 and a gas outflow passage 26, having a fastening member 3 for fastening installing this diaphragm 4 and having a valve operation member 5 for opening and closing the opening 252 by contacting with the diaphragm 4 from the outside, a ceramic push-contact member 41 is fixed to an integrally formed holding part in the diaphragm 4 to improve corrosion resistant performance of the diaphragm 4.