A method of making a guide wire involves butting a connection end face at a proximal end of a first wire against a connection end face at a distal end of a second wire while applying voltage and a pressing force to weld together the first and second wires at a welded portion. The welded portion forms a projection that projects outwardly in an outer peripheral direction relative to portions of the first and second wire adjacent the projection. The outer dimension of the projection at the welded portion is adjusted so that upon completing adjusting the outer dimension of the projection the projection still projects outwardly in the outer peripheral direction relative to the portions of the first and second wire adjacent the projection.