A hot-pressed member comprising: a steel sheet; and a surface layer disposed on a surface of the steel sheet, the steel sheet having a chemical composition containing, in mass%, C: 0.28% or greater and less than 0.50%, Si: 0.01% or greater and 1.5% or less, Mn: 1.0% or greater and 2.2% or less, P: 0.05% or less, S: 0.005% or less, Al: 0.01% or greater and 0.50% or less, N: 0.01% or less, Sb: 0.001% or greater and 0.020% or less, and one or more selected from Mo: 0.005% or greater and 0.35% or less, Cr: 0.005% or greater and 0.35% or less, Nb: 0.001% or greater and 0.05% or less, Ti: 0.001% or greater and 0.05% or less, B: 0.0002% or greater and 0.0050% or less, Ca: 0.005% or less, V: 0.05% or less, Cu: 0.50% or less, Ni: 0.50% or less, and Sn: 0.50% or less, with a balance being Fe and incidental impurities, wherein, in the hot-pressed member, the steel sheet has a microstructure in which a prior austenite average grain diameter is 8 μm or less, and martensite is present in a volume fraction of 95% or greater in a region within 30 μm of the surface of the steel sheet of the hot-pressed member, a Ni diffusion region having a thickness of 0.5 μm or greater exists in the surface layer, a standard deviation of Vickers hardness values of the hot-pressed member is 35 or less, Mndif in mass% in a sheet thickness direction = Mnmax in mass% Mnmin in mass% ≤ 0.20, where Mndif in mass% is a degree of Mn segregation, Mnmax in mass% is a maximum value of amounts of Mn measured by EPMA line analysis in a sheet thickness direction, and Mnmin in mass% is a minimum value of the amounts of Mn measured by EPMA line analysis in a sheet thickness direction, and the hot-pressed member has a tensile strength of 1780 MPa or greater measured in accordance with JIS Z 2241 as defined in the description. a steel sheet; and a surface layer disposed on a surface of the steel sheet, the steel sheet having a chemical composition containing, in mass%, C: 0.28% or greater and less than 0.50%, Si: 0.01% or greater and 1.5% or less, Mn: 1.0% or greater and 2.2% or less, P: 0.05% or less, S: 0.005% or less, Al: 0.01% or greater and 0.50% or less, N: 0.01% or less, Sb: 0.001% or greater and 0.020% or less, and one or more selected from Mo: 0.005% or greater and 0.35% or less, Cr: 0.005% or greater and 0.35% or less, Nb: 0.001% or greater and 0.05% or less, Ti: 0.001% or greater and 0.05% or less, B: 0.0002% or greater and 0.0050% or less, Ca: 0.005% or less, V: 0.05% or less, Cu: 0.50% or less, Ni: 0.50% or less, and Sn: 0.50% or less, Mo: 0.005% or greater and 0.35% or less, Cr: 0.005% or greater and 0.35% or less, Nb: 0.001% or greater and 0.05% or less, Ti: 0.001% or greater and 0.05% or less, B: 0.0002% or greater and 0.0050% or less, Ca: 0.005% or less, V: 0.05% or less, Cu: 0.50% or less, Ni: 0.50% or less, and Sn: 0.50% or less, with a balance being Fe and incidental impurities, wherein, in the hot-pressed member, the steel sheet has a microstructure in which a prior austenite average grain diameter is 8 μm or less, and martensite is present in a volume fraction of 95% or greater in a region within 30 μm of the surface of the steel sheet of the hot-pressed member, a Ni diffusion region having a thickness of 0.5 μm or greater exists in the surface layer, a standard deviation of Vickers hardness values of the hot-pressed member is 35 or less, Mndif in mass% in a sheet thickness direction = Mnmax in mass% Mnmin in mass% ≤ 0.20, where Mndif in mass% is a degree of Mn segregation, Mnmax in mass% is a maximum value of amounts of Mn measured by EPMA line analysis in a sheet thickness direction, and Mnmin in mass% is a minimum value of the amounts of Mn measured by EPMA line analysis in a sheet thickness direction, and Mndif in mass% is a degree of Mn segregation, Mnmax in mass% is a maximum value of amounts of Mn measured by EPMA line analysis in a sheet thickness direction, and Mnmin in mass% is a minimum value of the amounts of Mn measured by EPMA line analysis in a sheet thickness direction, and the hot-pressed member has a tensile strength of 1780 MPa or greater measured in accordance with JIS Z 2241 as defined in the description.