A spark plug comprising: an insulator having an axial hole along an axial line; a center electrode that is provided in the axial hole; a cylindrical metal shell that is disposed around an outer periphery of the insulator; and a ground electrode whose base end is fixed to the metal shell, wherein a distal end portion of the ground electrode includes a first surface that faces a side of the center electrode, a second surface that faces a side that is opposite to the first surface, and an inclined surface that is formed continuously with a distal end of the first surface and is inclined with respect to the second surface such that a thickness of the ground electrode decreases towards a distal end side of the ground electrode, and wherein a noble metal tip is joined to the inclined surface such that part of the noble metal tip is buried in the inclined surface, wherein a width of the inclined surface is larger than a width of the noble metal tip, and wherein, when a distance from a distal end of the ground electrode to a proximal-end-side end portion of the inclined surface is A and a distance from the distal end of the ground electrode to a proximal-end-side end portion of the noble metal tip is B, A ≥ B, characterized in that the inclined surface is a planar surface, wherein an inclination angle (θ) of the inclined surface with respect to the second surface is less than or equal to 6 degrees, and wherein a burying amount of the noble metal tip along the axial line from the proximal-end-side end portion of the inclined surface is greater than or equal to 0.2 mm. an insulator having an axial hole along an axial line; a center electrode that is provided in the axial hole; a cylindrical metal shell that is disposed around an outer periphery of the insulator; and a ground electrode whose base end is fixed to the metal shell, wherein a distal end portion of the ground electrode includes a first surface that faces a side of the center electrode, a second surface that faces a side that is opposite to the first surface, and an inclined surface that is formed continuously with a distal end of the first surface and is inclined with respect to the second surface such that a thickness of the ground electrode decreases towards a distal end side of the ground electrode, and a first surface that faces a side of the center electrode, a second surface that faces a side that is opposite to the first surface, and an inclined surface that is formed continuously with a distal end of the first surface and is inclined with respect to the second surface such that a thickness of the ground electrode decreases towards a distal end side of the ground electrode, and wherein a noble metal tip is joined to the inclined surface such that part of the noble metal tip is buried in the inclined surface, wherein a width of the inclined surface is larger than a width of the noble metal tip, and wherein, when a distance from a distal end of the ground electrode to a proximal-end-side end portion of the inclined surface is A and a distance from the distal end of the ground electrode to a proximal-end-side end portion of the noble metal tip is B, A ≥ B, characterized in that the inclined surface is a planar surface, wherein an inclination angle (θ) of the inclined surface with respect to the second surface is less than or equal to 6 degrees, and wherein a burying amount of the noble metal tip along the axial line from the proximal-end-side end portion of the inclined surface is greater than or equal to 0.2 mm.