A sensor includes a detector element including a detecting portion and an element back portion on which two or more electrical connection terminal portions are formed; two or more connection terminals which each include an oblong frame main body that extends in an axial direction and an element contact portion that is electrically connected to a corresponding one of the electrical connection terminal portions; a separator that accommodates the connection terminals and the element back portion; and a base that surrounds an outer periphery of the separator. The separator includes a partition wall that is made of a resin material and partitions a plurality of accommodation spaces from each other. The accommodation spaces include an element accommodation space that accommodates portions of the element contact portions and the element back portion, and a plurality of terminal accommodation spaces which each accommodate one of the two or more frame main bodies.