A spark plug includes a center electrode, a ground electrode, and a noble metal tip. The noble metal tip is joined to an object member of at least one of two electrodes via a fusion zone. A projected overlap region of the noble metal tip and the fusion zone accounts for 70% or more of a projected region of the noble metal tip. The object member contains at least Si out of Al and Si such that the amount of Si is 0.4% by mass or higher and such that the total amount of Al and Si is 0.5% by mass. Multi-fusion spots exist on the surface of the fusion zone. Segments of a baseline which pass through the respective multi-fusion spots have a total length of a predetermined percentage of the length of the baseline. Joining strength to the noble metal tip can thereby be greatly improved when the member to be joined contains Si.