PURPOSE: A gas sensor which can measure low concentration of nitric oxide gas at a high precision is provided to precisely measure a target gas and to increase durability and a response rate. CONSTITUTION: A gas sensor comprises a sensor body(106), first and second gas inlets(101,102) and a measuring unit(105). The first and second gas inlets are formed in the sensor body. The measuring unit has a chamber structure inside the sensor body. The nitric oxide gas from the first and second gas inlets is mixed in the chamber structure. The measuring unit measures the concentration of the disassembled oxygen gas from the nitric oxide gas. The measuring unit is arranged between the first and second gas inlets.
