Gas sensing element

A gas sensing element comprising a solid electrolytic substrate, a measuring objective gas side electrode provided on a surface of said solid electrolytic substrate, and a reference electrode provided on another surface of said solid electrolytic substrate, wherein

• said measuring objective gas side electrode is exposed to a chamber;
• a gas introducing passage is provided for connecting said chamber to an external environment of said gas sensing element;
• a diffusion resistive layer, which is made of a porous member, covers an outer opening portion of said gas introducing passage at an external environment side of said gas introducing passage, with no additional diffusion resistive member provided on an outer surface of said diffusion resistive layer;
• and
• a relationship S/Ld≦1.5 is established
• where S represents a cross-sectional area of an inner open end of said gas introducing passage opening to said chamber, L represents a circumferential length of said inner open end of said gas introducing passage, and d represents a thickness of said chamber in the vicinity of said inner open end of said gas introducing passage.