In a cross section of the gas sensor element which is perpendicular to its lengthwise direction and through which all first to fourth lead portions penetrate, when the cross section is bisected into two regions with respect to the width direction of the gas sensor element, the first lead portion and the fourth lead portion are disposed in one of the regions and the second lead portion and the third lead portion are disposed in the other region, and the second lead portion and the third lead portion are disposed so as to be spaced apart from each other in the width direction with no overlap as viewed in a stacking direction.