A gas sensor is provided which comprises a sensor element for detecting a component of a gas and a cup-shaped protector for covering a detecting section of the sensor element. The protector is dual-walled and have cup-shaped inner and outer protector members. The inner and outer protector members are constructed and arranged so that g1>g2 where g1 is the distance between an inner surface of a circumferential wall of the outer protector member and an outer surface of a circumferential wall of the inner protector member and g2 is the distance between an inner surface of a bottom wall of the outer protector member and an outer surface of a bottom wall of the inner protector member. The outer protector member has at the circumferential wall thereof a plurality of first gas holes. The inner protector member has at the circumferential wall thereof a plurality of second gas holes.