Sensor element and gas sensor

A sensor element comprising:

• a layered body that includes a plurality of stacked layers of an oxygen ion-conductive solid electrolyte, and that includes a measurement-object gas flowing portion which a measurement-object gas is introduced and flowed in;
• a measurement electrode provided on an inner peripheral surface of the measurement-object gas flowing portion;
• a measurement-object gas side electrode provided in a region of the layered body that is exposed to the measurement-object gas;
• a reference electrode that is formed inside of the layered body;
• and
• a reference gas introducing layer disposed at least in part between two layers of the plurality of stacked layers and made of a porous material having pores that introduces a reference gas being used as a standard for detection of a specific gas concentration in the measurement-object gas and that flows the reference gas to the reference electrode, the reference gas introducing layer including an inlet portion that is located at a rear end of the sensor element serving as an inlet of the reference gas and one or more gas flowing spaces that are different from the pores provided over a region from the inlet portion to the reference electrode in a direction in which the reference gas is flowed.