PURPOSE: To prevent the surface flaw of a metallic strip by concaving supporting rolls and supporting only the edges of the continuously moving metallic strip on the rolls in a linear contact state.

CONSTITUTION: A metallic strip 5 of a Cu alloy or the like enters an annealing furnace 1 from the inlet and exits from the outlet. A plurality of chambers 2 for blowing hot air are installed in the furnace 1, and a plurality of supporting rolls 4 for supporting the strip 5 are arranged among the chambers 2. Centrally concaved rolls are used as rolls 4. Accordingly, the strip 5 contacts with the rolls 4 only at the edges, so the furnace flaw of the strip 5 is not generated.