A manufacturing method for an ignition plug is provided. The method includes: preparing an insulator having a cavity provided at a leading end portion thereof by disposing a leading end of the center electrode more inwards than a leading end of the insulator; building the insulator in an interior of the metal shell such that the leading end of the insulator is situated closer to a rear end side than the leading end of the metal shell; removing at least part of a leading end portion of the metal shell which projects from a leading end face of the insulator; and disposing the ground electrode at the leading end portion of the metal shell and welding the ground electrode and the metal shell together after the removal step.