To provide a gas valve of a simple structure in which a gas flow rate can be controlled lineally in a wide range, the pressure and flow velocity of the gas can be controlled.

When a magnetic assembly 10 moves downwards, the gas pressures on both sides of a main diaphragm 3 becomes uniform, and the main diaphragm 3 is closed to stop the gas flow in the gas valve. When the magnetic assembly 10 moves upwards, the gas flows into the first cell 101, the second cell 102, and the forth cell 104. The gas flowing in the second cell 102 flows into a third cell 103 to apply pressure on the bottom of the diaphragm 3. Gas flowing from an inlet 151 is divided into two, the main diaphragm 3 is push- opened by the pressure of the main gas, the main gas flows out to an outlet 161, gas flowing into the fourth cell 104 flows to a regulation lever 17 when a servo motor 25 is actuated, a regulation screw 19 is operated, thus the pressure and the flow velocity of the gas flowing out of the outlet 161 are controlled.