GAS SENSOR ELEMENT

A gas sensor element capable of preventing a decrease in responsiveness despite a protective layer covering a gas introduction opening is provided. A gas sensor element according to an aspect of the present invention includes an element base having a surface in which a gas introduction opening is open, a protective layer, a buffer layer, and a gas introduction layer that is disposed between the element base and the buffer layer. The gas introduction layer covers the gas introduction opening, is in contact with the protective layer, and has a porosity that is 30% or more and is higher by 5% or more than the porosity of the buffer layer.