In this study, we developed micro gas valves which can control the gas pressure inside microfluidic systems in a simple and passive way. We designed a microfluidic chip having a liquid reservoir, a gas chamber and a microchannel connecting them to demonstrate both a micro relief valve and a micro regulator on a chip. We fabricated and tested the microfluidic chip to check the feasibility of the proposed micro valves. Test results show that when the gas pressure is greater than the relief pressure the micro relief valve discharges the gas decreasing the system pressure down to the atmospheric pressure. Also, the micro regulator kept the system pressure constant regardless of the degree of the over-pressure at pressure source. The proposed valves would be good candidates for cheap and reliable gas pressure controller in various microfluidic systems using gases.