A gas sensor element is composed of a sensor section, a heater section, and a porous protective layer. The sensor section is composed of a solid electrolyte layer and a pair of electrodes. The heater section heats the sensor section to activate it. The porous protective layer covers surfaces of the sensor section and the heater section of the gas sensor element in a gas sensor which is exposed to a target detection gas to be detected. The porous protective layer is made of a mixture of hydrophobic heat resisting particles having a contact angle of not less than 75° to a drop of water, and the hydrophilic heat resisting particles having a contact angle not more than 30° to a drop of water. A gas sensor equipped with the above gas sensor element is also disclosed.