A steel sheet having a chemical composition comprising, by mass%, C: 0.05 to 0.40%, Si: 0.2 to 3.0%, Mn: 0.1 to 5.0%, sol. Al: 0 to less than 0.4000%, P: 0.0300% or less, S: 0.0300% or less, N: 0.0100% or less, B: 0 to 0.010%, Ti: 0 to 0.150%, Nb: 0 to 0.150%, V: 0 to 0.150%, Cr: 0 to 2.00%, Ni: 0 to 2.00%, Cu: 0 to 2.00%, Mo: 0 to 1.00%, W: 0 to 1.00%, Ca: 0 to 0.100%, Mg: 0 to 0.100%, Zr: 0 to 0.100%, Hf: 0 to 0.100%, REM: 0 to 0.100% and a balance of Fe and impurities, wherein a surface layer of the steel sheet contains grain boundary oxides, a Ratio A of a length of the grain boundary oxides projected on a surface of the steel sheet to a length of the surface of the steel sheet when examining a cross-section of the surface layer of the steel sheet is 50% or more and 100% or less, a number density of granular oxides is less than 4.0/μm 2, wherein "granular oxides" means oxides dispersed as grains inside the crystal grains of the steel or on the crystal grain boundaries and "granular" means being present away from each other mutually in the steel matrix, having a 1.0 to 5.0 aspect ratio, the steel sheet comprises an Si-Mn depleted layer having a thickness of 3.0 μm or more from the surface of the steel sheet, wherein the thickness of the Si-Mn depleted layer means the distance from the surface of the steel sheet to the furthest position where a grain boundary oxide is present when proceeding from the surface of the steel sheet, or in the case of a plated steel sheet, the interface of the steel sheet and plating layer, in the thickness direction of the steel sheet, i.e., direction vertical to surface of steel sheet, and Si and Mn contents of the Si-Mn depleted layer at 1/2 position of the thickness and not containing oxides are respectively less than 10% of the Si and Mn contents at a sheet thickness center part of the steel sheet, wherein the Ratio A, the number density of granular oxides, the thickness of the Si-Mn depleted layer and the Si and Mn contents are determined in accordance with the description. C: 0.05 to 0.40%, Si: 0.2 to 3.0%, Mn: 0.1 to 5.0%, sol. Al: 0 to less than 0.4000%, P: 0.0300% or less, S: 0.0300% or less, N: 0.0100% or less, B: 0 to 0.010%, Ti: 0 to 0.150%, Nb: 0 to 0.150%, V: 0 to 0.150%, Cr: 0 to 2.00%, Ni: 0 to 2.00%, Cu: 0 to 2.00%, Mo: 0 to 1.00%, W: 0 to 1.00%, Ca: 0 to 0.100%, Mg: 0 to 0.100%, Zr: 0 to 0.100%, Hf: 0 to 0.100%, REM: 0 to 0.100% and a balance of Fe and impurities, wherein a surface layer of the steel sheet contains grain boundary oxides, a Ratio A of a length of the grain boundary oxides projected on a surface of the steel sheet to a length of the surface of the steel sheet when examining a cross-section of the surface layer of the steel sheet is 50% or more and 100% or less, a number density of granular oxides is less than 4.0/μm 2, wherein "granular oxides" means oxides dispersed as grains inside the crystal grains of the steel or on the crystal grain boundaries and "granular" means being present away from each other mutually in the steel matrix, having a 1.0 to 5.0 aspect ratio, the steel sheet comprises an Si-Mn depleted layer having a thickness of 3.0 μm or more from the surface of the steel sheet, wherein the thickness of the Si-Mn depleted layer means the distance from the surface of the steel sheet to the furthest position where a grain boundary oxide is present when proceeding from the surface of the steel sheet, or in the case of a plated steel sheet, the interface of the steel sheet and plating layer, in the thickness direction of the steel sheet, i.e., direction vertical to surface of steel sheet, and Si and Mn contents of the Si-Mn depleted layer at 1/2 position of the thickness and not containing oxides are respectively less than 10% of the Si and Mn contents at a sheet thickness center part of the steel sheet, wherein the Ratio A, the number density of granular oxides, the thickness of the Si-Mn depleted layer and the Si and Mn contents are determined in accordance with the description.