A gas sensor element including a lead portion (79a) formed on a lower surface of an insulating member (76) and extending through a through hole (176) to an upper surface thereof, and a lead portion (79b) extending from the upper surface of the insulating member (76) through the through hole (176) to the lower surface of the insulating member (76) so as to cover the lead portion (79a) along the inner circumferential wall and a portion of the lower surface around the through hole. The lead portion (79a) has a section exposed to a space (230) on the lower surface side of the insulating member (76). The lead portion (79b) is disposed so as to face the insulating member (76) with the space (230) therebetween. The lead portion (79a) communicates with the outside through the space (230). Also disclosed is a method for producing the gas sensor element.