Gas sensor

A gas sensor comprising:

• a sensor element extending in a direction of an axial line and including a rear end portion having an outer surface, and an electrode pad on the outer surface;
• a metal terminal member extending in the direction of the axial line and including:
• a forward metal terminal member electrically connected to the electrode pad and including a rear-end connection portion;
• and
• a rear metal terminal member including a forward end portion connected to the rear-end connection portion of the forward metal terminal member in an overlapping manner, a central portion located rearward of the forward end portion, and a lead-wire connection portion located rearward of the central portion;
• a tubular separator which holds the metal terminal member and surrounds the rear end portion of the sensor element;
• and
• a lead wire including a distal end portion connected to the lead-wire connection portion of the rear metal terminal member, and extending rearward of the tubular separator,
• wherein the forward end portion and the central portion are integrally connected through a first neck portion smaller in sectional area orthogonal to the direction of the axial line than the forward end portion and the central portion, and the central portion and the lead-wire connection portion are integrally connected through a second neck portion smaller in sectional area orthogonal to the direction of the axial line than the central portion and the lead-wire connection portion, and
• the first neck portion is greater in moment of inertia of area orthogonal to the direction of the axial line than the second neck portion.