Disclosed is a spark plug 100 with a built-in resistor comprises an insulator 2 having an axially extending passing-through-hole 6, a terminal metal fitting 13 fixed within the passing-through-hole 6 at an end thereof, a center electrode 3 fixed within the same passing-through-hole at the other end thereof and a resistor 15 provided between the terminal metal fitting 13 and the center electrode 3 within the passing-through-hole 6. A surface layer region including the surface of the center electrode 3 which is exposed to the resistor 15 is a metallic layer 30 formed of a metal based on at least one of Zn, Sn, Pb, Rh, Pd, Pt, Cu, Au, Sb and Ag or a Ni alloy containing at least one of B and P, so that the center electrode 3 is provided in direct contact with the resistor 15 on the surface of the metallic layer 30.