Gas sensor element and gas sensor

A cross-sectional shape of a gap of a gas sensor element has an end point A which is one of contact points at which the cross-sectional shape is in single-point contact with a virtual straight line parallel to a lamination direction, the one contact point being closest to one side of the laminated structure, an end point B which is one of the contact points closest to another side of the laminated structure, an end point C having the greatest separation from a straight line AB toward a solid electrolyte ceramic layer, and an end point D having the greatest separation from the straight line AB toward another ceramic layer. The distance H1 between the straight line AB and the end point C and the distance H2 between the straight line AB and the end point D satisfy 0.25≦H1/H2