A spark plug comprises: a spark plug housing; an axial core electrode disposed in a longitudinal direction in the spark plug housing; and a ground electrode having a terminal part spaced apart along the longitudinal direction from a distal end of the axial core electrode and disposed in a perpendicular relation with the axial core electrode, the terminal part having a circular through hole formed along an axis coaxial with the axial core electrode, the circular through hole having a tapered inner surface and including a plurality of spiral protrusions disposed on the tapered inner surface to induce a turbulent air flow in the combustion inflow.