Gassensor

A gas sensor includes a sensor element body having a porous layer provided on an outer surface, and a power supply device which supplies power to a heater element that is in the sensor element body. The amount of power being applied to the heater element by the power supply device when gas detection is being performed by the gas sensor in a steady state is designated as P [W], the volume of the length range of a heating region of the heater element provided in the sensor element body as V [mm3], and the applied power density as X [W/mm3], where X is a value expressed by P/V. In that case, the following relationship is satisfied between the applied power density X and the average thickness Y [μm] of the porous layer:Y≥509.32−2884.89X+5014.12X2