A sensor includes a sensor element and a conductive wire. The sensing element includes a sensing portion and a terminal wire extending from the sensing portion. The sensing portion has an electrical characteristic that changes in accordance with a change in an atmosphere. The conductive wire is for communicating an electrical signal from the sensor element. The conductive wire includes a plurality of conductors twisted together. The terminal wire and the conductive wire are arranged in a longitudinal direction of the sensor and are connected to each other by welding. The conductive wire includes a first weld portion formed by integrating the plurality of conductors in the longitudinal direction by welding. The terminal wire and the conductive wire are connected to each other through a second weld portion, and the second weld portion is formed only in a region longitudinally overlapping the first weld portion.