In a gas sensor, when an arithmetical mean roughness Ra of an inner periphery of a metal tube 95 is 1 μm or less and end portions 93 and 94 of U-springs 92 are formed as curved contact portions, the end portions 93 and 94 of the U-springs 92 can slide smoothly along the inner periphery of the metal tube 95. Therefore, when vibration is applied to the gas sensor, the U-springs 92 can be prevented from being caught in the inner periphery of the metal tube 95, and the vibration can be absorbed by an elastic function of the U-springs 92. Even if the gas sensor vibrates, defective contact between a sensor element 20 and contact fittings 71 and wear and cracks in the sensor element 20 are less likely to occur. That is, the gas sensor resistant to vibration can be obtained.