A spark plug has a housing, a pair of center and ground electrodes configured to define a spark gap therebetween, a guide member and an oblique surface. The ground electrode has a standing portion that stands distalward from a distal end of the housing. The guide member is configured to guide the flow of an air-fuel mixture in a combustion chamber of an engine to the spark gap. The guide member protrudes distalward from the distal end of the housing at a different circumferential position from the ground electrode. The oblique surface is formed at the distal end of the housing so as to be circumferentially positioned between the guide member and the standing portion of the ground electrode. The oblique surface is oblique to the axial direction of the spark plug so that the radial distance between the oblique surface and the center electrode decreases in the distalward direction.