PURPOSE: To provide a structure of electrode and a method for forming the same, which is made of a soft metal such as indium or tin and which is used in a convergence ion beam device, in particular a one to form a galium convergence ion beam.

CONSTITUTION: A soft metal to constitute an electrode is subjected to processing not as machining with a lathe or a milling machine but as forging with attention paid on the low melting point of the material, wherein the material is tightly attached to the metal material of a base board to establish a structure in which a low melting point metal layer 33 having an opening 32 narrower than an opening 30 provided in the base board is laid over the same 31.