A gas sensor including a gas sensor element, and an inner member surrounding the gas sensor element. The gas sensor element has a detection element having therein a space to which a gas to be measured is introduced, and a heater laminated on the detection element. The detection element includes a first oxygen pumping cell for pumping oxygen into or out of the space, an oxygen concentration detection cell, a detection electrode and a reference electrode. In side faces of the detection element along a laminating direction, a region from a front end of the inner member to a part of the detection electrode along a longitudinal direction is covered with a glass coat having a glass transition point of over 700° C. Further the detection electrode is controlled at a temperature range from 600° C. or more to not more than the glass transition point of the glass coat.