A spark plug including: an insulator having a through hole extending in an axial direction, the through hole including, a first portion and a second portion provided on a rear end side of the first portion, the second portion having a larger diameter than that of the first portion; a center electrode provided in the first portion; an external terminal provided in the second portion; and a sintered ceramic resistor provided in the second portion. The sintered ceramic resistor is formed from a sintered body of a conductive ceramic, connecting the center electrode and the external terminal electrically, and having a length in an axial direction of 40% or more of a length in an axial direction of the second portion of the through hole.