This method of producing an amorphous transformer for electric power supply comprises forming and shaping an iron core by laminating amorphous alloy thin bands and forming a winding, subjecting the iron core, after forming and shaping, to an annealing treatment in which a temperature of a center portion of the iron core during annealing is 300 to 340° C. and a holding time is not less than 0.5 hr, and applying a magnetic field having a strength of not less than 800 A/m to the iron core while subjecting the iron core, after forming and shaping, to the annealing treatment.