A surface layer grain refining hot-shearing method comprising: heating and keeping a steel sheet having a carbon content of 0.15% or more by mass in a temperature range of from Ac3 to 1400°C to austenitize the steel sheet; subsequently shearing the steel sheet in a state in which the steel sheet is placed on a die; and quenching by rapidly cooling the sheared steel sheet, wherein a start temperature of the shearing is set to be a temperature (°C) obtained by adding a temperature of from 30°C to 140°C to a previously measured Ar3 of the steel sheet; or wherein a start temperature of the shearing is set to be a temperature (°C) obtained by adding a value, which is calculated by multiplying an amount of equivalent plastic strain of a surface layer in a sheared portion by a coefficient from 40 to 60, to a previously measured Ar3 of the steel sheet, wherein the amount of equivalent plastic strain of the surface layer in the sheared portion is calculated as an average value of an amount of equivalent plastic strain of a region in a range of from 5% to 20% of a thickness of the steel sheet from a shear plane of the sheared portion to an inside of the steel sheet in a normal direction of the shear plane and in a range of from 20% to 50% of the thickness of the steel sheet in a thickness direction of the steel sheet from a bottom on a burr side of the sheared portion, and wherein the amount of equivalent plastic strain of the surface layer in the sheared portion is calculated by a shearing simulation by analysis using a finite element method that is performed based on a stress-strain diagram at a steel sheet temperature of from 500°C to 800°C, by integrating an increment in equivalent plastic strain "dε-P" by a Mises yield function that is represented by the following Formula when a material coordinate system is defined as x, y, and z: d ε ̅ P = 2 3 d ε xx 2 + d ε yy 2 + d ε zz 2 + 2 d ε xy 2 + 2 d ε yz 2 + 2 d ε zx 2 heating and keeping a steel sheet having a carbon content of 0.15% or more by mass in a temperature range of from Ac3 to 1400°C to austenitize the steel sheet; subsequently shearing the steel sheet in a state in which the steel sheet is placed on a die; and quenching by rapidly cooling the sheared steel sheet, wherein a start temperature of the shearing is set to be a temperature (°C) obtained by adding a temperature of from 30°C to 140°C to a previously measured Ar3 of the steel sheet; or wherein a start temperature of the shearing is set to be a temperature (°C) obtained by adding a value, which is calculated by multiplying an amount of equivalent plastic strain of a surface layer in a sheared portion by a coefficient from 40 to 60, to a previously measured Ar3 of the steel sheet, wherein the amount of equivalent plastic strain of the surface layer in the sheared portion is calculated as an average value of an amount of equivalent plastic strain of a region in a range of from 5% to 20% of a thickness of the steel sheet from a shear plane of the sheared portion to an inside of the steel sheet in a normal direction of the shear plane and in a range of from 20% to 50% of the thickness of the steel sheet in a thickness direction of the steel sheet from a bottom on a burr side of the sheared portion, and wherein the amount of equivalent plastic strain of the surface layer in the sheared portion is calculated by a shearing simulation by analysis using a finite element method that is performed based on a stress-strain diagram at a steel sheet temperature of from 500°C to 800°C, by integrating an increment in equivalent plastic strain "dε-P" by a Mises yield function that is represented by the following Formula when a material coordinate system is defined as x, y, and z: d ε ̅ P = 2 3 d ε xx 2 + d ε yy 2 + d ε zz 2 + 2 d ε xy 2 + 2 d ε yz 2 + 2 d ε zx 2