A method of producing a spark plug comprises (a) a step of combining a metallic shell and an insulator; (b) a step of inserting a portion of the assembly on its forward end side into a pressure container; (c) a step of bringing an insulating member into contact with the outer circumferential surface of a base side portion of the insulator over the entire circumference thereof, and pressing the assembly so as to close the opening by the assembly; and (d) a step of pressurizing the interior of the pressure container and applying a predetermined voltage between the terminal electrode and the metallic shell, wherein the step (b) includes a step of inserting the portion of the assembly on the forward end side into the pressure container such that a gap formed between the outer surface of the insulator and the inner surface of the metallic shell on the forward end side of the assembly is disposed in the pressure container.