A spark plug 5 for an internal combustion engine includes a center electrode 1, an insulator 2, and a housing 3. The insulator 2 includes a distal end side exposed part and an insulator enlarged diameter part 21. The housing 3 includes a lateral electrode 32, an engaging part 33, and a crimping portion 35. A buffer member 4 that restrains the distal end side exposed part 20 by pressing a part of the distal end side exposed part 20 toward the center and a part of the inner peripheral surface of the lateral electrode 32 in a radial direction at a distal end side of the engaging part 33 is disposed at a base end side of the gas pocket 230.