Gas sensor element and gas sensor

A gas sensor element comprising:

• an element body portion which includes a plurality of laminated ceramic sheets;
• a pump cell which is configured to adjust a concentration of oxygen in a gas to be measured which is introduced into the element body portion;
• a detection chamber which is formed inside the element body portion and into which the gas to be measured in which the concentration of oxygen has been adjusted is introduced;
• and
• a layer-shaped cathode electrode which is housed in the detection chamber and configured to decompose NO, wherein
• a relationship between a volume V1 of the detection chamber and a volume V2 of the cathode electrode satisfies either a condition (A) or a condition (B) described below,
• Condition (A):
• the volume V1 is not less than 0.047 mm3 and not greater than 0.057 mm3 and the volume V2 is not less than 0.031 mm3 and not greater than 0.047 mm3, and
• Condition (B):
• the volume V1 is not less than 0.057 mm3 and not greater than 0.117 mm3 and the volume V2 is not less than 0.047 mm3 and not greater than 0.059 mm3.