A spark plug include an insulator, a central electrode, which is in the form of a bar received in the insulator, a metal case, which surrounds the insulator and is grounded, and a ground elbow fixed to the metal case. The central electrode includes a discharge terminal exposed outside the insulator and defining an extension line as an imaginary line extending from the discharge terminal along a central axis of the central electrode. The ground elbow has a connection end and an opposite, sharp-tip-like receiving end. The connection end is fixed to the metal case. The receiving end is set close to but spaced from the discharge terminal and is locate by one side of the extension line.