Disclosed is a spark plug capable of preventing electrode wear while ensuring impact resistance. In the spark plug, a conductive seal is arranged between a rear end portion of a center electrode and a resistor within an axial hole of an insulator. The conductive seal includes a side-surface seal layer brought into contact with the whole of a side surface of the rear end portion of the center electrode and having a thickness of 10 μm or larger in an axis perpendicular direction. Assuming that a projection area is defined by projecting the center electrode onto the axial hole in the axis perpendicular direction around a center axis of the spark plug, a contact surface of the resistor brought into contact with the axial hole overlaps at last a part of the projection area.