A primary object of the present invention is to provide a method for manufacturing Cu-Sn coexisting steel where a good quality of its surface is kept even if hot-rolled.
In the present invention, in a case where Cu-Sn coexisting steel is manufactured by continuous casting of molten steel that contains C: 0.04 to 0.20%, Si: 0.05 to 1.00%, Mn: 0.20 to 2.50%, P: no more than 0.05%, S: no more than 0.02%, Cu: 0.20 to 1.50% and Sn: 0.06 to 0.50% and further contains Al: 0.06 to 1.00% and Ni: 0.05 to 1.00% by mass, and Fe and impurities as the remainder, the composition of the molten steel is adjusted so as to satisfy [Al]/(3[Si] + [Mn]) ≥ 0.050, [Ni]/([Cu] + 5[Sn]) ≥ 0.10 and [Al]/[Ni] ≥ 0.20 if the content of an element X in the molten steel is represented as [X], an internal oxidation layer is formed by oxidizing a surface of a slab in a process of cooling the slab, and Al 2 O 3 is contained by composite oxides that are generated in the internal oxidation layer.