A spark plug includes: a mounting bracket; a center electrode having a first end portion exposed and extended from first end portion of the mounting bracket; a slant-shape ground electrode that has first end side joined to the first end portion of the mounting bracket, has a surface of the second end side extended to be opposed to the first end portion of the center electrode, and has an extension direction inclined with respect to the center electrode; a convex portion protruding from a base material of the ground electrode on the surface thereof toward the center electrode, inclines toward the center electrode with respect to a protrusion direction, and has a convex portion opposed surface opposed to an end surface of the center electrode; and a precious metal layer formed on at least the convex portion opposed surface out of surfaces of the convex portion.