To provide an air exhaust valve equipped with the same function as an air relief circuit capable of performing air relief from a pneumatic apparatus without using a complicated air relief circuit.

The air exhaust valve is composed of a valve seat 14 installed in a flow passage tying a primary side port 12 to a secondary side port 13, a valve member 17 to open and close the valve seat 14, a spring 28 to energize resiliently the valve member 17 in the valve closing direction, a valve opening/ closing rod 21 to put the valve member 17 in the opening/closing motions, an operation button 40 to release the valve member 17 by moving the rod 21, a piston 33 coupled with the rod 21, a pressure chamber 36 formed at one side of the piston 33, and a communication passage 37 to lead the secondary air to the pressure chamber 36.