Spark plug

A spark plug comprising:

• a cylindrical metallic shell having a ground electrode at a forward end of the cylindrical metallic shell;
• a cylindrical insulator held in the metallic shell;
• a center electrode disposed in the insulator, the center electrode generating spark discharge in a gap between the ground electrode and the center electrode;
• a resistor element disposed in the insulator and having a forward end located rearward of a rear end of the center electrode;
• a forward-end-side electrically conductive seal layer disposed in the insulator to be located between the center electrode and the resistor element;
• and
• a rear-end-side electrically conductive seal layer disposed in the insulator to be located rearward of the resistor element, wherein
• the forward end of the resistor element is located forward of a rear end of the metallic shell, and
• a rear end of the resistor element is located rearward of the rear end of the metallic shell.