A martensitic stainless steel comprising a chemical composition containing, in mass%: C: 0.020 % or more and less than 0.10 %, Si: more than 0.3% and 2.0 % or less, Mn: 0.01 % or more and 3.0 % or less, P: 0.050 % or less, S: 0.050 % or less, Cr: 10.0 % or more and 16.0 % or less, Ni: 0.01 % or more and 0.80 % or less, Nb: 0.002 % or more and less than 0.050 %, V: 0.01 % or more and less than 0.10 %, Al: 0.001 % or more and 0.50 % or less, and N: more than 0.050 % and 0.20 % or less, and optionally one or more selected from Cu: 0.01 % or more and 5.0 % or less, Mo: 0.01 % or more and 0.50 % or less, Co: 0.01 % or more and 0.50 % or less, Ti: 0.01 % or more and 0.50 % or less, Zr: 0.01 % or more and 0.50 % or less, B: 0.0002 % or more and 0.0100 % or less, Ca: 0.0002 % or more and 0.0100 % or less, and Mg: 0.0002 % or more and 0.0100 % or less, and when Cu is 1.0 % or more, Mn is 0.01 % or more and 1.0 % or less, satisfying the following relational expressions to , and the balance being Fe and incidental impurities, 5 × C % ≥ N % ≥ C % Nb % + V % ≤ C % + N % C % + N % ≥ 0.10 % wherein C %, N %, Nb % and V % indicate respectively the contents of C, N, Nb and V (mass%) in the steel, wherein 80% or more of the volume of the entire structure of the martensitic stainless steel is in a martensite phase and the balance is in a ferrite phase and/or a retained austenite phase, wherein the martensitic stainless steel has a tensile strength of 1200 MPa or more, an elongation of 7.5 % or more, and an ultimate deformability of 0.7 or more, measured in a room temperature tensile test according to JIS Z2241, and wherein the room temperature tensile test is carried out according to the method provided in the description, and the elongation and the ultimate deformability are calculated by the expressions provided in the description. C: 0.020 % or more and less than 0.10 %, Si: more than 0.3% and 2.0 % or less, Mn: 0.01 % or more and 3.0 % or less, P: 0.050 % or less, S: 0.050 % or less, Cr: 10.0 % or more and 16.0 % or less, Ni: 0.01 % or more and 0.80 % or less, Nb: 0.002 % or more and less than 0.050 %, V: 0.01 % or more and less than 0.10 %, Al: 0.001 % or more and 0.50 % or less, and N: more than 0.050 % and 0.20 % or less, and optionally one or more selected from Cu: 0.01 % or more and 5.0 % or less, Mo: 0.01 % or more and 0.50 % or less, Co: 0.01 % or more and 0.50 % or less, Ti: 0.01 % or more and 0.50 % or less, Zr: 0.01 % or more and 0.50 % or less, B: 0.0002 % or more and 0.0100 % or less, Ca: 0.0002 % or more and 0.0100 % or less, and Mg: 0.0002 % or more and 0.0100 % or less, and when Cu is 1.0 % or more, Mn is 0.01 % or more and 1.0 % or less, satisfying the following relational expressions to , and the balance being Fe and incidental impurities, 5 × C % ≥ N % ≥ C % Nb % + V % ≤ C % + N % C % + N % ≥ 0.10 % wherein C %, N %, Nb % and V % indicate respectively the contents of C, N, Nb and V (mass%) in the steel, wherein 80% or more of the volume of the entire structure of the martensitic stainless steel is in a martensite phase and the balance is in a ferrite phase and/or a retained austenite phase, wherein the martensitic stainless steel has a tensile strength of 1200 MPa or more, an elongation of 7.5 % or more, and an ultimate deformability of 0.7 or more, measured in a room temperature tensile test according to JIS Z2241, and wherein the room temperature tensile test is carried out according to the method provided in the description, and the elongation and the ultimate deformability are calculated by the expressions provided in the description. <EOS>