Spark plug for internal combustion engine

A spark plug for an internal combustion engine, comprising:

• a cylindrical housing;
• a cylindrical insulator held inside the housing;
• a center electrode held inside the insulator such that a distal end portion thereof projects from the insulator;
• a terminal metal fitting held inside the insulator such that a proximal end portion thereof projects from the insulator;
• a ground electrode disposed so as to form a spark discharge gap with the center electrode;
• a resistor disposed inside the insulator so as to be located between the center electrode and the terminal metal fitting;
• a first conductive sealing material filled in a space surrounded by the resistor, the terminal metal fitting and the insulator;
• and
• a second conductive insulating material filled in a space surrounded by the resistor, the center electrode and the insulator, wherein
• the terminal metal fitting includes an engaging portion engaged into an inner peripheral surface of the proximal end portion of the insulator and a small-diameter portion extending from the engaging portion and having a diameter smaller than a diameter of the engaging portion,
• the small-diameter portion is formed with ribs extending in an axial direction of the small-diameter portion and projecting outward from an outer peripheral surface of the small-diameter portion, and
• the first conductive sealing member is located at least at part on a distal end side of a gap between an outer peripheral surface of the terminal metal fitting and the inner peripheral surface of the insulator.