Spark plug

A spark plug, comprising:

• a cylindrical insulator extending in the direction of an axis of the spark plug;
• an annular plate packing;
• and
• a cylindrical metal shell arranged circumferentially around the insulator,
• the insulator including a step portion formed on an outer circumferential surface thereof and having an outer diameter decreasing toward the front in the direction of the axis and a leg portion located front of the step portion and extending toward the front in the direction of the axis,
• the metal shell including a taper portion formed on an inner circumferential surface thereof and having an inner diameter decreasing toward the front in the direction of the axis,
• the insulator being fixed in the metal shell by crimping a rear end portion of the metal shell with the step portion of the insulator retained on the taper portion of the metal shell via the plate packing,
• the insulator further including a curved surface portion formed in a concave shape on the outer circumferential surface thereof at a position between the step portion and the leg portion,
• 50% or more of an inner circumferential edge portion of the plate packing in a circumferential direction thereof being in contact with a part of the insulator located front of a middle region between front and rear ends of the curved surface portion.