A transformer apparatus and a transformer shielding method are provided for shielding external electronic noises and protecting against erosion. The transformer apparatus comprises a toroidal core, a primary winding, a secondary winding, a protection tape, a metal foil, and an UL tube. The primary winding and the secondary winding are wound around the toroidal core at opposite side to each other. The protection tape is wrapped around the primary winding and the secondary winding. The metal foil encloses the protection tape. The UL tube enfolds the metal foil. The transformer shielding method comprises wrapping a primary winding and a secondary winding of the transformer apparatus by a protection tape, enclosing the protection tape by a metal foil, and enfolding the metal foil by an UL tube.