A gas sensor element and a related manufacturing method are disclosed. The gas sensor element comprises a
solid electrolyte body 11, having
oxygen ion conductivity, which has both surfaces formed with a measuring gas detecting
electrode and a reference gas detecting
electrode, respectively, and a
porous layer, covering the measuring gas detecting
electrode and permeating measuring gases, which is formed using a
porous layer green sheet containing fibrous organic materials, oriented in a direction substantially perpendicular to a thickness direction thereof, which are caused to burn down to form a coarse layer with large
porosity in one area closer to the
solid electrolyte and a dense layer with less
porosity than that of the coarse layer in the other area remote from the
solid electrolyte body to provide capability of permeating measuring gases in a direction perpendicular to a thickness direction of the
porous layer.