A spark plug including a center electrode and a ground electrode. A center electrode noble metal tip is joined to a leading end portion of a center electrode, and a ground electrode noble metal tip is joined to a center-electrode-side side surface of the ground electrode. A distal end portion of the ground electrode noble metal tip protrudes from a distal-end surface of the ground electrode by 0.1 mm to 1.5 mm. A center-electrode-side side surface of the ground electrode noble metal tip projects from a center-electrode-side side surface by 0.15 mm to 0.6 mm. The ground electrode includes chamfered portions. Thickness lengths and widthwise lengths of the respective chamfered portions achieved within a cross section perpendicular to a center axis of the ground electrode are set to 0.2 mm or more.