Sensor element and gas sensor

A sensor element comprising:

• an element main body which has a plurality of oxygen-ion-conductive solid electrolyte layers stacked and in which a flow portion of a measurement-object gas is disposed so as to introduce and pass the measurement-object gas;
• a measurement electrode disposed in the flow portion of the measurement-object gas;
• a measurement electrode lead having a first portion that is connected to the measurement electrode and that is disposed in the flow portion of the measurement-object gas and a second portion that is connected to the first portion and that is embedded in the element main body;
• a hermetic layer that is part of the element main body and that surrounds an end region of the second portion including a border with the first portion;
• and
• a lead insulating layer that is part of the element main body and that surrounds at least part of the second portion excluding the end region,
• wherein a length L of the end region in the second portion is 0.25 mm or more, the length L being from the border with the first portion to a front end of the lead insulating layer in a length direction of the measurement electrode lead, when viewed in a stacking direction of the plurality of solid electrolyte layers, and
• wherein the length L is 2 mm or less.