A steel sheet comprising: an inner layer; and a hard layer at one or both surfaces of the inner layer, wherein the hard layer consists of, by mass%, C: 0.08 to 0.40%, Si: 0.01 to 3.00%, Mn: 1.000 to 10.00%, P: 0.0001 to 0.0200%, S: 0.0001 to 0.0200%, and optionally, by mass%, Al: 0.500% or less, N: 0.0200% or less, Cr: 2.000% or less, Mo: 1.000% or less, O: 0.0200% or less, Ti: 0.500% or less, B: 0.0100% or less, Nb: 0.500% or less, V: 0.500% or less, Cu: 0.500% or less, W: 0.100% or less, Ta: 0.100% or less, Ni: 0.500% or less, Sn: 0.050% or less, Sb: 0.050% or less, As: 0.050% or less, Mg: 0.0500% or less, Ca: 0.050% or less, Y: 0.050% or less, Zr: 0.050% or less, La: 0.050% or less, Ce: 0.050% or less, and a balance of Fe and impurities, the inner layer consists of, by mass%, C: 0.001 to 0.200%, Si: 0.01 to 3.00%, Mn: 0.20 to 3.00%, P: 0.0001 to 0.0200%, S: 0.0001 to 0.0200%, and optionally, by mass%, Al: 0.500% or less, N: 0.0200% or less, Cr: 2.000% or less, Mo: 1.000% or less, O: 0.0200% or less, Ti: 0.500% or less, B: 0.0100% or less, Nb: 0.500% or less, V: 0.500% or less, Cu: 0.500% or less, W: 0.100% or less, Ta: 0.100% or less, Ni: 0.500% or less, Sn: 0.050% or less, Sb: 0.050% or less, As: 0.050% or less, Mg: 0.0500% or less, Ca: 0.050% or less, Y: 0.050% or less, Zr: 0.050% or less, La: 0.050% or less, Ce: 0.050% or less, and a balance of Fe and impurities, the hard layer has a thickness of 20 μm or more and 2/5 of the total sheet thickness or less, the hard layer has an average micro-Vickers hardness of 400HV or more and less than 700HV, the hard layer has an N amount of 0.02% or less, the inner layer has an average micro-Vickers hardness of 80HV or more and less than 400HV, the inner layer has a carbide volume ratio of less than 2.00%, and the hard layer has a nanohardness standard deviation of 2.00 or less; wherein the thickness of the hard layer, the average micro-Vickers hardness, the carbide volume ratio and the nanohardness standard deviation are measured as described in the description. the hard layer consists of, by mass%, C: 0.08 to 0.40%, Si: 0.01 to 3.00%, Mn: 1.000 to 10.00%, P: 0.0001 to 0.0200%, S: 0.0001 to 0.0200%, and optionally, by mass%, Al: 0.500% or less, N: 0.0200% or less, Cr: 2.000% or less, Mo: 1.000% or less, O: 0.0200% or less, Ti: 0.500% or less, B: 0.0100% or less, Nb: 0.500% or less, V: 0.500% or less, Cu: 0.500% or less, W: 0.100% or less, Ta: 0.100% or less, Ni: 0.500% or less, Sn: 0.050% or less, Sb: 0.050% or less, As: 0.050% or less, Mg: 0.0500% or less, Ca: 0.050% or less, Y: 0.050% or less, Zr: 0.050% or less, La: 0.050% or less, Ce: 0.050% or less, and a balance of Fe and impurities, C: 0.08 to 0.40%, Si: 0.01 to 3.00%, Mn: 1.000 to 10.00%, P: 0.0001 to 0.0200%, S: 0.0001 to 0.0200%, and optionally, by mass%, Al: 0.500% or less, N: 0.0200% or less, Cr: 2.000% or less, Mo: 1.000% or less, O: 0.0200% or less, Ti: 0.500% or less, B: 0.0100% or less, Nb: 0.500% or less, V: 0.500% or less, Cu: 0.500% or less, W: 0.100% or less, Ta: 0.100% or less, Ni: 0.500% or less, Sn: 0.050% or less, Sb: 0.050% or less, As: 0.050% or less, Mg: 0.0500% or less, Ca: 0.050% or less, Y: 0.050% or less, Zr: 0.050% or less, La: 0.050% or less, Ce: 0.050% or less, and a balance of Fe and impurities, the inner layer consists of, by mass%, C: 0.001 to 0.200%, Si: 0.01 to 3.00%, Mn: 0.20 to 3.00%, P: 0.0001 to 0.0200%, S: 0.0001 to 0.0200%, and optionally, by mass%, Al: 0.500% or less, N: 0.0200% or less, Cr: 2.000% or less, Mo: 1.000% or less, O: 0.0200% or less, Ti: 0.500% or less, B: 0.0100% or less, Nb: 0.500% or less, V: 0.500% or less, Cu: 0.500% or less, W: 0.100% or less, Ta: 0.100% or less, Ni: 0.500% or less, Sn: 0.050% or less, Sb: 0.050% or less, As: 0.050% or less, Mg: 0.0500% or less, Ca: 0.050% or less, Y: 0.050% or less, Zr: 0.050% or less, La: 0.050% or less, Ce: 0.050% or less, and a balance of Fe and impurities, C: 0.001 to 0.200%, Si: 0.01 to 3.00%, Mn: 0.20 to 3.00%, P: 0.0001 to 0.0200%, S: 0.0001 to 0.0200%, and optionally, by mass%, Al: 0.500% or less, N: 0.0200% or less, Cr: 2.000% or less, Mo: 1.000% or less, O: 0.0200% or less, Ti: 0.500% or less, B: 0.0100% or less, Nb: 0.500% or less, V: 0.500% or less, Cu: 0.500% or less, W: 0.100% or less, Ta: 0.100% or less, Ni: 0.500% or less, Sn: 0.050% or less, Sb: 0.050% or less, As: 0.050% or less, Mg: 0.0500% or less, Ca: 0.050% or less, Y: 0.050% or less, Zr: 0.050% or less, La: 0.050% or less, Ce: 0.050% or less, and a balance of Fe and impurities, the hard layer has a thickness of 20 μm or more and 2/5 of the total sheet thickness or less, the hard layer has an average micro-Vickers hardness of 400HV or more and less than 700HV, the hard layer has an N amount of 0.02% or less, the inner layer has an average micro-Vickers hardness of 80HV or more and less than 400HV, the inner layer has a carbide volume ratio of less than 2.00%, and the hard layer has a nanohardness standard deviation of 2.00 or less; wherein the thickness of the hard layer, the average micro-Vickers hardness, the carbide volume ratio and the nanohardness standard deviation are measured as described in the description.