Steel sheet, member, method for producing same, method for producing hot-rolled steel sheet for cold-rolled steel sheet, and method for producing cold-rolled steel sheet

Provided are: a steel sheet having a tensile strength (TS) of 780 MPa or more and excellent collision characteristics; a member; and methods for producing the steel sheet and the member. A steel sheet having a component composition in which the carbon equivalent (CE) satisfies 0.46% or more and a specific steel structure, the average crystal grain size of ferrite being 25 [mu] m or less, and the variation coefficient (CV) of the ferrite grain size * the carbon equivalent (CE) being 0.28 or less, when the steel sheet is bent 90 DEG in the rolling (L) direction with the width (C) direction as the axis under the conditions of curvature radius/sheet thickness of 4.2 and then bent back to be flattened again, the ratio (NF void/NF) of ferrite crystal grains having voids at the interface with respect to all of the ferrite crystal grains in an L-cross-section in a region 0-50 [mu] m from the surface of the steel sheet on the compression-tensile deformation side is 15% or less. The tensile strength of the steel sheet