A pneumatic valve provided within a valve casing a seal member ; a shaft provided with a valve body capable of abutting against the seal member ; and a closing actuating pressure chamber to which a closing actuating gas is supplied, and which moves the shaft in an axial direction to actuate the valve body to a closed state, wherein the shaft includes a first member that receives pressure from the closing actuating pressure chamber , and a second member that includes the valve body and is movable relative to the first member in the axial direction, wherein the pneumatic valve further comprises a stopper that is provided in the valve casing in a movement path of the first member , and a first biasing member that is sandwiched between the first member and the second member , wherein the first biasing member is configured to have an elastic energy accumulated therein in a state where the first member is in contact with the stopper , and is configured to press the valve body against the seal member ; characterized in that the pneumatic valve is configured so that: when the closing actuating gas is supplied to the closing actuating pressure chamber , an internal pressure of the closing actuating pressure chamber is raised, the shaft is moved in the axial direction toward the sealing member , and the valve body is in contact with the seal member in a state where the first member is not locked to the stopper ; and when the internal pressure of the closing actuating pressure chamber further increases from the state where the valve body is in contact with the seal member and the first member is not locked to the stopper , the first member is moved in the axial direction toward the seal member until the first member is locked to the stopper ; and the first biasing member is configured so that a first length of the first biasing member in the axial direction when the valve body is in contact with the seal member and the first member is not locked to the stopper is longer than a second length of the first biasing member in the axial direction when the valve body is in contact with the seal member and the first member is locked to the stopper . when the closing actuating gas is supplied to the closing actuating pressure chamber , an internal pressure of the closing actuating pressure chamber is raised, the shaft is moved in the axial direction toward the sealing member , and the valve body is in contact with the seal member in a state where the first member is not locked to the stopper ; and when the internal pressure of the closing actuating pressure chamber further increases from the state where the valve body is in contact with the seal member and the first member is not locked to the stopper , the first member is moved in the axial direction toward the seal member until the first member is locked to the stopper ; and the first biasing member is configured so that a first length of the first biasing member in the axial direction when the valve body is in contact with the seal member and the first member is not locked to the stopper is longer than a second length of the first biasing member in the axial direction when the valve body is in contact with the seal member and the first member is locked to the stopper . <EOS>