A gas sensor in which respective terminal leads are fitted and connected to respective electrodes on inner and outer circumferential surface of a hollow, cup-shaped detection element When a leading end connecting portion of a terminal lead (71, 91) is disposed on the front end side of a separator (111) and an intermediate portion (74, 94) extending from the rear end of the leading end connecting portion is inserted into a hole (113), a spring tab (77, 97) provided on the intermediate portion (74, 94) is pressed against a second wall surface (117) of the hole (113), whereby an engagement portion (76, 96) is pressed against a first wall surface opposite the second wall surface (117). The first projection (118) is formed on the first wall surface of the hole (113) so that it can come into contact with and support a first face (76b, 96b) of the engagement portion (76, 96) on opposing lateral sides of the spring tab (77, 97).