PURPOSE: To easily obtain the frame parts of a pair of spectacles having excellent flexibility, by a method wherein a base material comprising a plurality of elements constituting an alloy showing superelasticity is clad and the clad material is processed into a desired shape to be subjected to diffusion heat treatment.

CONSTITUTION: A Ti-material and an Ni-material for constituting an alloy showing superelasticity or a Cu-Zn alloy material and an Ni-material for constituting a Cu-Zn-Ni alloy are connected to form a clad material. The clad material is processed into a product shape or a shape approximate thereto to be subjected to diffusion heat treatment and each material is diffused and formed into a solid solution to obtain the frame parts of spectacles comprising an alloy having a composition showing superelasticity. By this method, parts each having a complicated shape or parts each having a fine shape can be easily prepared.