Magnetic properties and domain structure were investigated for die-drawn and subsequently annealed Fe-Si-B amorphous wires. It was found that the die-drawn wire has a bamboo domain similar to that of the Co based wire with negative magnetostriction and looses the re-entrant flux reversal characteristic. It was also found that the wire recovers the re-entrant characteristic after annealing. The tension-annealed wire has clear shell and core domain structure and exhibits the re-entrant characteristic with enhanced remanence. The surface bamboo domain layer as thin as 5 /spl mu/m was connected to the core domain by magnetization that changes direction continuously between two domains without a domain wall. From the temperature dependence of a threshold field for the discontinuous flux jump, it is inferred that the re-entrant characteristic is caused by the depinning of the reverse domain existing near the wire end due to demagnetizing effect.