A gas sensor includes a gas sensor element having a detection portion, a metallic shell holding the gas sensor element, and a tubular body made of metal, which is welded in a state of being externally fitted to a front side or a rear side of the metallic shell. In the present invention, the tubular body is tightly fitted to a tapered portion that is provided at an outer surface of the metallic shell and is radially narrowed toward the tubular body. The tubular body is welded at the tapered portion.