A steel sheet includes: a base iron; a scale of 10.0 μm or less in thickness on a surface of the base iron; a subscale between the base iron and the scale. In the subscale, an average value of Cr concentrations is 1.50 mass % to 5.00 mass %, and one part or more exist(s) where a ratio of Cr concentrations between two adjacent measurement regions separate by 1 μm is 0.90 or less or 1.11 or more in a range of 50 μm in length in a rolling direction. A percentage of an amount of Ti contained in carbide or carbonitride of 100 nm or more and 1 μm or less in grain diameter to a parameter Tieff represented by a formula “Tieff=[Ti]−48/14[N]” is 30% or less in which [Ti] denotes a Ti content (mass %) and [N] denotes a N content (mass %).