A Pb-free hot-dip Sn—Zn coated steel sheet comprising a hot-dip coating layer comprised of 1 to 8.8 wt % of Zn and the balance of Sn in an amount of 91.2 to 99.0 wt % and unavoidable impurities and/or ancillary ingredients on the surface of steel sheet, the coating surface having Sn dendrite crystals and Sn dendrite arm spacings buried by an Sn—Zn two-way eutectic structure, an area ratio of Sn dendrites in the coating surface being 5 to 90%, and the arm spacing of the Sn dendrites being not more than 0.1 mm, preferably having a discontinuous FeSn2 alloy phase at the surface of the steel sheet.