A ferritic stainless steel for exhaust system components excellent in corrosion resistance after heating, the ferritic stainless steel consisting of: 0.002 mass% to 0.015 mass% of C; 0.002 mass% to 0.02 mass% of N; 0.03 mass% to 1.0 mass% of Si; 0.05 mass% to 1.0 mass% of Mn; 0.04 mass% or less of P; 0.01 mass% or less of S; 11.0 mass% to 22.5 mass% of Cr; 0.02 mass% to 0.5 mass% of Sn; 0.003 mass% to 0.2 mass% of Al; one or both of 0.03 mass% to 0.35 mass% of Ti and 0.03 mass% to 0.6 mass% of Nb; and optionally one or more of 0.05 mass% to 1.5 mass% of Cu; 0.1 mass% to 1.2 mass% of Ni; 0.03 mass% to 3 mass% of Mo; 0.03 mass% to 1 mass% of W; 0.05 mass% to 0.5 mass% of V; 0.01 mass% to 0.5 mass% of Sb; 0.03 mass% to 0.5 mass% of Zr; 0.02 mass% to 0.2 mass% of Co; 0.0002 mass% to 0.002 mass% of Ca; 0.0002 mass% to 0.002 mass% of Mg; 0.0002 mass% to 0.005 mass% of B; 0.001 mass% to 0.01 mass% of REM; 0.0002 mass% to 0.01 mass% of Ga; and 0.01 mass% to 0.5 mass% of Ta; and a remnant consisting of Fe and inevitable impurities, wherein a grain size number on a surface of the ferritic stainless steel is 6 or more, wherein the grain size on a Z-surface, which is a surface parallel to the surface, is measured according to JIS G0551, and wherein the ferritic stainless steel is heated in the atmosphere under a condition satisfying a formula, exp − 23000 / T × t ≥ 4.3 × 10 − 15 and the upper limit of the value represented by the left side of the formula is 4.5 × 10 -9; where T represents a temperature in K and t represents a time in s, to obtain 2 to 15 nm of a Sn-concentrated layer containing Sn at a concentration twice or more of a Sn concentration in a base material, the Sn-concentrated layer being present on the ferritic stainless steel, and wherein the Sn-concentrated layer is present at and near a border between an oxide film and a base material. 0.002 mass% to 0.015 mass% of C; 0.002 mass% to 0.02 mass% of N; 0.03 mass% to 1.0 mass% of Si; 0.05 mass% to 1.0 mass% of Mn; 0.04 mass% or less of P; 0.01 mass% or less of S; 11.0 mass% to 22.5 mass% of Cr; 0.02 mass% to 0.5 mass% of Sn; 0.003 mass% to 0.2 mass% of Al; one or both of 0.03 mass% to 0.35 mass% of Ti and 0.03 mass% to 0.6 mass% of Nb; and optionally one or more of 0.05 mass% to 1.5 mass% of Cu; 0.1 mass% to 1.2 mass% of Ni; 0.03 mass% to 3 mass% of Mo; 0.03 mass% to 1 mass% of W; 0.05 mass% to 0.5 mass% of V; 0.01 mass% to 0.5 mass% of Sb; 0.03 mass% to 0.5 mass% of Zr; 0.02 mass% to 0.2 mass% of Co; 0.0002 mass% to 0.002 mass% of Ca; 0.0002 mass% to 0.002 mass% of Mg; 0.0002 mass% to 0.005 mass% of B; 0.001 mass% to 0.01 mass% of REM; 0.0002 mass% to 0.01 mass% of Ga; and 0.01 mass% to 0.5 mass% of Ta; and a remnant consisting of Fe and inevitable impurities, wherein a grain size number on a surface of the ferritic stainless steel is 6 or more, wherein the grain size on a Z-surface, which is a surface parallel to the surface, is measured according to JIS G0551, and wherein the ferritic stainless steel is heated in the atmosphere under a condition satisfying a formula, exp − 23000 / T × t ≥ 4.3 × 10 − 15 and the upper limit of the value represented by the left side of the formula is 4.5 × 10 -9; where T represents a temperature in K and t represents a time in s, to obtain 2 to 15 nm of a Sn-concentrated layer containing Sn at a concentration twice or more of a Sn concentration in a base material, the Sn-concentrated layer being present on the ferritic stainless steel, and wherein the Sn-concentrated layer is present at and near a border between an oxide film and a base material.