A spark plug comprising a center electrode, a ground electrode, and a noble metal tip resistance-welded to at least one of the center electrode and the ground electrode, wherein the noble metal tip has a flat discharge surface, a bottom surface which is concave toward the discharge surface and embedded in the electrode to which the noble metal tip is resistance-welded, and a side surface whose width increases from the discharge surface toward the bottom surface; on a predetermined cross section containing a vertical line passing through the centroid of the discharge surface, a maximum thickness along a direction parallel to the vertical line is defined as the maximum thickness t of the noble metal tip, and a straight line which passes through a portion (Phmax) of the bottom surface where the noble metal tip has the maximum thickness and is parallel to the discharge surface is defined as a first straight line; on a first half cross section of two half cross sections formed by dividing the predetermined cross section by the vertical line, a maximum width along a direction orthogonal to the vertical line is defined as the maximum width Rw1 of the noble metal tip, a distance between the first straight line and a position where the noble metal tip has the maximum width, the distance being measured along a direction parallel to the vertical line, is defined as a warpage height h1 of the noble metal tip, and a distance from an intersection (CA, CA1) between the vertical line and the discharge surface to an end portion of the discharge surface is defined as a width Rt1 of the discharge surface; on a second half cross section of the two half cross sections which differs from the first half cross section, a maximum width along the direction orthogonal to the vertical line is defined as the maximum width Rw2 of the noble metal tip, a distance between the first straight line and a position where the noble metal tip has the maximum width, the distance being measured along the direction parallel to the vertical line, is defined as a warpage height h2 of the noble metal tip, and a distance from an intersection (CA, CA1) between the vertical line and the discharge surface to an end portion of the discharge surface is defined as a width Rt2 of the discharge surface; and relations h1/t ≤ 0.2 and Rw1/Rt1 ≥ 1.03 are satisfied, and relations h2/t ≤ 0.2 and Rw2/Rt2 ≥ 1.03 are satisfied. the noble metal tip has a flat discharge surface, a bottom surface which is concave toward the discharge surface and embedded in the electrode to which the noble metal tip is resistance-welded, and a side surface whose width increases from the discharge surface toward the bottom surface; on a predetermined cross section containing a vertical line passing through the centroid of the discharge surface, a maximum thickness along a direction parallel to the vertical line is defined as the maximum thickness t of the noble metal tip, and a straight line which passes through a portion (Phmax) of the bottom surface where the noble metal tip has the maximum thickness and is parallel to the discharge surface is defined as a first straight line; on a first half cross section of two half cross sections formed by dividing the predetermined cross section by the vertical line, a maximum width along a direction orthogonal to the vertical line is defined as the maximum width Rw1 of the noble metal tip, a distance between the first straight line and a position where the noble metal tip has the maximum width, the distance being measured along a direction parallel to the vertical line, is defined as a warpage height h1 of the noble metal tip, and a distance from an intersection (CA, CA1) between the vertical line and the discharge surface to an end portion of the discharge surface is defined as a width Rt1 of the discharge surface; on a second half cross section of the two half cross sections which differs from the first half cross section, a maximum width along the direction orthogonal to the vertical line is defined as the maximum width Rw2 of the noble metal tip, a distance between the first straight line and a position where the noble metal tip has the maximum width, the distance being measured along the direction parallel to the vertical line, is defined as a warpage height h2 of the noble metal tip, and a distance from an intersection (CA, CA1) between the vertical line and the discharge surface to an end portion of the discharge surface is defined as a width Rt2 of the discharge surface; and relations h1/t ≤ 0.2 and Rw1/Rt1 ≥ 1.03 are satisfied, and relations h2/t ≤ 0.2 and Rw2/Rt2 ≥ 1.03 are satisfied.