A sensor device includes an element cover at the tip end of a housing, retaining a sensor element. An outer cover is provided with outer side holes, with the tip position of the outer side holes being farther toward the tip end than is the tip position of an inner cover, and a first flow passage having a gas flow direction that is at right angles to the axial direction is formed at the inner side of the outer cover. An inner side hole in the inner cover is open to a second flow passage provided between the side surfaces of the inner cover and the outer cover, and a detection surface of the sensor element is located on an extension line in an extension direction of a guide member which extends obliquely into the interior of the inner cover from the tip-position edge of the inner side hole.