A spark plug 1 includes a tubular housing 2, a tubular insulator 3 held inside the housing 2, a center electrode 4 held inside the insulator 3 such that a distal end portion 41 protrudes, a ground electrode 5 that forms a spark discharge gap G between it and the center electrode 4, and a standing member 6 that stands distalward from a distal end portion 21 of the housing 2. In at least one of a pair of side surfaces 61 of the standing member 6 which face in a plug circumferential direction, there is formed a guide step portion 62 for guiding the flow of an air-fuel mixture in a combustion chamber of an internal combustion engine to the spark discharge gap G.