A coated steel sheet comprising a steel sheet and a coating layer provided on at least a part of a surface of the steel sheet, wherein: the coating layer has a chemical composition comprising in terms of % by mass: Al: from 15% to 60% Mg: from 0.5% to 8.0% Sn: from 0.5% to 20.0% Si: from 0.05% to 1.50% Bi: from 0% to 5.0%, In: from 0% to 2.0%, Ca: from 0% to 3.0%, Y: from 0% to 0.5%, La: from 0% to 0.5%, Ce: from 0% to 0.5%, Cr: from 0% to 0.25%, Ti: from 0% to 0.25%, Ni: from 0% to 0.25%, Co: from 0% to 0.25%, V: from 0% to 0.25%, Nb: from 0% to 0.25%, Cu: from 0% to 0.25%, Mn: from 0% to 0.25%, Sr: from 0% to 0.5%, Sb: from 0% to 0.5%, Pb: from 0% to 0.5%, B: from 0% to 0.5%, and a balance consisting of Zn and impurities, wherein: the coating layer has a granular Mg 2 Sn phase-containing structure in an area fraction of from 5 to 65%, a structure containing a solid solution of Zn and Al in an area fraction of from 35% to 95%, a massive MgZn 2 phase with an equivalent circle diameter of 1 μm or more in an area fraction of from 0% to 20%, a massive Zn phase with an equivalent circle diameter of 2 μm or more in an area fraction of from 0% to 20%, and a Zn/Al/MgZn 2 ternary eutectic structure in an area fraction of from 0% to 3%; and the granular Mg 2 Sn phase-containing structure is a structure constituted with a Zn phase and a granular Mg 2 Sn phase having a crystal grain size of less than 1 μm dispersed in the Zn phase. the coating layer has a chemical composition comprising in terms of % by mass: Al: from 15% to 60% Mg: from 0.5% to 8.0% Sn: from 0.5% to 20.0% Si: from 0.05% to 1.50% Bi: from 0% to 5.0%, In: from 0% to 2.0%, Ca: from 0% to 3.0%, Y: from 0% to 0.5%, La: from 0% to 0.5%, Ce: from 0% to 0.5%, Cr: from 0% to 0.25%, Ti: from 0% to 0.25%, Ni: from 0% to 0.25%, Co: from 0% to 0.25%, V: from 0% to 0.25%, Nb: from 0% to 0.25%, Cu: from 0% to 0.25%, Mn: from 0% to 0.25%, Sr: from 0% to 0.5%, Sb: from 0% to 0.5%, Pb: from 0% to 0.5%, B: from 0% to 0.5%, and a balance consisting of Zn and impurities, wherein: the coating layer has a granular Mg 2 Sn phase-containing structure in an area fraction of from 5 to 65%, a structure containing a solid solution of Zn and Al in an area fraction of from 35% to 95%, a massive MgZn 2 phase with an equivalent circle diameter of 1 μm or more in an area fraction of from 0% to 20%, a massive Zn phase with an equivalent circle diameter of 2 μm or more in an area fraction of from 0% to 20%, and a Zn/Al/MgZn 2 ternary eutectic structure in an area fraction of from 0% to 3%; and the granular Mg 2 Sn phase-containing structure is a structure constituted with a Zn phase and a granular Mg 2 Sn phase having a crystal grain size of less than 1 μm dispersed in the Zn phase. the coating layer has a granular Mg 2 Sn phase-containing structure in an area fraction of from 5 to 65%, a structure containing a solid solution of Zn and Al in an area fraction of from 35% to 95%, a massive MgZn 2 phase with an equivalent circle diameter of 1 μm or more in an area fraction of from 0% to 20%, a massive Zn phase with an equivalent circle diameter of 2 μm or more in an area fraction of from 0% to 20%, and a Zn/Al/MgZn 2 ternary eutectic structure in an area fraction of from 0% to 3%; and the granular Mg 2 Sn phase-containing structure is a structure constituted with a Zn phase and a granular Mg 2 Sn phase having a crystal grain size of less than 1 μm dispersed in the Zn phase.