A spark plug includes a ground electrode and a center electrode, at least one of which includes an electrode body, an electrode tip, and a weld part formed therebetween. The weld part has an orthogonal projection on a virtual plane perpendicular to a layering direction of the electrode body and the electrode tip. The orthogonal projection includes projecting portions extending in a specific direction. The weld part satisfies a condition that a first line segment is shorter than a second line segment, wherein: the first line segment is a virtual line segment connecting peaks of adjacent two projecting portions; and the second line segment is a virtual line segment that is perpendicular to the first line segment and connects the first line segment to an outer periphery of the weld part at a point farthest from the first line segment.