To prevent a recess from being generated in a welded portion, even when welding both end parts of a band material by beam welding, in a manufacturing method of manufacturing a belleville spring from the band material.

The band material 10 is formed ring-likely by bending molding. The band material 10 is constituted to make a material of the band material arranged in the welding portion get larger than a material of the band material arranged in an other portion. The both end parts of the band material 10 formed ring-likely are welded by means of a beam 26. Protrusions are formed on both faces of the welded portion 28 after welded.